# Patent

## Title
VLIW image processor

## Abstract

A microcontroller for an image sensing and processing apparatus is provided. The microcontroller has VLIW processor circuitry, image sensor interface circuitry connected between the VLIW processor circuitry and the image sensor, bus interface circuitry connected between the VLIW processor circuitry and a bus connectable with devices other than the image sensor, and buffer memory and queuing circuitry intermediate the image sensor and bus interface circuitry and the VLIW processor to control delivery of information to the VLIW processor.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This is a Continuation of U.S. application Ser. No. 10/485,738 filed on Feb. 4, 2004, herein incorporated by reference.


FIELD OF THE INVENTION
The present invention relates to an image sensing apparatus. In particular, the present invention relates to an image sensing apparatus and to a microcontroller for an image sensing apparatus.
BACKGROUND OF THE INVENTION
Recently, digital printing technology has been proposed as a suitable replacement for traditional camera and photographic film techniques. The traditional film and photographic techniques rely upon a film roll having a number of pre-formatted negatives which are drawn past a lensing system and onto which is imaged a negative of a image taken by the lensing system. Upon the completion of a film roll, the film is rewound into its container and forwarded to a processing shop for processing and development of the negatives so as to produce a corresponding positive set of photos.
Unfortunately, such a system has a number of significant drawbacks. Firstly, the chemicals utilized are obviously very sensitive to light and any light impinging upon the film roll will lead to exposure of the film. They are therefore required to operate in a light sensitive environment where the light imaging is totally controlled. This results in onerous engineering requirements leading to increased expense. Further, film processing techniques require the utilizing of a “negative” and its subsequent processing onto a “positive” film paper through the utilization of processing chemicals and complex silver halide processing etc. This is generally unduly cumbersome, complex and expensive. Further, such a system through its popularity has lead to the standardization on certain size film formats and generally minimal flexibility is possible with the aforementioned techniques.
Recently, all digital cameras have been introduced. These camera devices normally utilize a charge coupled device (CCD) or other form of photosensor connected to a processing chip which in turn is connected to and controls a media storage device which can take the form of a detachable magnetic card. In this type of device, the image is captured by the CCD and stored on the magnetic storage device. At some later time, the image or images that have been captured are down loaded to a computer device and printed out for viewing. The digital camera has the disadvantage that access to images is non-immediate and the further post processing step of loading onto a computer system is required, the further post processing often being a hindrance to ready and expedient use.
At present, hardware for image processing demands processors that are capable of multi-media and high resolution processing. In this field, VLIW microprocessor chips have found favor rather than the Reduced Instruction Set Computer (RISC) chip or the Complex Instruction Set Computer (CISC) chip.
By way of background, a CISC processor chip can have an instruction set of well over 80 instructions, many of them very powerful and very specialized for specific control tasks. It is common for the instructions to all behave differently. For example, some might only operate on certain address spaces or registers, and others might only recognize certain addressing modes. This does result in a chip that is relatively slow, but that has powerful instructions. The advantages of the CISC architecture are that many of the instructions are macro-like, allowing the programmer to use one instruction in place of many simpler instructions. The problem of the slow speed has rendered these chips undesirable for image processing. Further, because of the macro-like instructions, it often occurs that the processor is not used to its full capacity.
The industry trend for general-purpose microprocessor design is for RISC designs. By implementing fewer instructions, the chip designed is able to dedicate some of the precious silicon real-estate for performance enhancing features. The benefits of RISC design simplicity are a smaller chip, smaller pin count, and relatively low power consumption.
Modern microprocessors are complex chip structures that utilize task scheduling and other devices to achieve rapid processing of complex instructions. For example, microprocessors for pre-Pentium type computers use RISC microprocessors together with pipelined superscalar architecture. On the other hand, microprocessors for Pentium and newer computers use CISC microprocessors together with pipelined superscalar architecture. These are expensive and complicated chips as a result of the many different tasks they are called upon to perform.
In application-specific electronic devices such as cameras, it is simply unnecessary and costly to incorporate such chips into these devices. However, image manipulation demands substantial processor performance. For this reason, Very Long Instruction Word processors have been found to be most suitable for the task. One of the reasons for this is that they can be tuned to suit image processing functions. This can result in an operational speed that is substantially higher than that of a desktop computer.
As is known, RISC architecture takes advantage of temporal parallelism by using pipelining and is limited to this approach. VLIW architectures can take advantage of spatial parallelism as well as temporal parallelism by using multiple functional units to execute several operations concurrently.
VLIW processors have multiple functional units connected through a globally shared register file. A central controller is provided that issues a long instruction word every cycle. Each instruction consists of multiple independent parallel operations. Further, each operation requires a statically known number of cycles to complete.
Instructions in VLIW architecture are very long and may contain hundreds of bits. Each instruction contains a number of operations that are executed in parallel. A compiler schedules operations in VLIW instructions. VLIW processes rely on advanced compilation techniques such as percolation scheduling that expose instruction level parallelism beyond the limits of basic blocks. In other words, the compiler breaks code defining the instructions into fragments and does complex scheduling. The architecture of the VLIW processor is completely exposed to the compiler so that the compiler has full knowledge of operation latencies and resource constraints of the processor implementation.
The advantages of the VLIW processor have led it to become a popular choice for image processing devices.
In FIG. 1A of the drawings, there is shown a prior art image processing device 1a that incorporates a VLIW microprocessor 2a. The microprocessor 1a includes a bus interface 3a. 
The device 1a includes a CCD (charge coupled device) image sensor 4a. The device 1a includes a CCD interface 5a so that the CCD can be connected to the bus interface 2a, via a bus 6a. As is known, such CCD's are analog devices. It follows that the CCD interface 5a includes an analog/digital converter (ADC) 7a. A suitable memory 35a and other devices 36a are also connected to the bus 2a in a conventional fashion.
In FIG. 1B of the drawings, there is shown another example of a prior art image processing device. With reference to FIG. 1A, like reference numerals refer to like parts, unless otherwise specified.
In this example, the image sensor is in the form of a CMOS image sensor 8a. Typically, the CMOS image sensor 8a is in the form of an active pixel sensor. This form of sensor has become popular lately, since it is a digital device and can be manufactured using standard integrated circuit fabrication techniques.
The CMOS image sensor 8a includes a bus interface 9a that permits the image sensor 8a to be connected to the bus interface 2a via the bus 6a. 
VLIW processors are generally, however, not yet the standard for digital video cameras. A schematic diagram indicating the main components of a digital video camera 10a is shown in FIG. 1C.
The camera 10a includes an MPEG encoder 11a that is connected to a microcontroller 12a. The MPEG encoder 11a and the microcontroller 12a both communicate with an ASIC (application specific integrated circuit) 13a that, in turn, controls a digital tape drive 14a. A CCD 15a is connected to the MPEG encoder 11a, via an ADC 16a and an image processor 17a. A suitable memory 18a is connected to the MPEG encoder 11a. 
In order for an image sensor device, be it a CCD or a CMOS Active Pixel Sensor (APS), to communicate with a VLIW processor, it is necessary for signals generated by an image sensor to be converted into a form which is readable by the VLIW processor. Further, control signals generated by the VLIW processor must be converted into a form that is suitable for reading by the image sensor.
In the case of a CCD device, this is done with a bus interface in combination with a CCD interface that includes an ADC. In the case of an APS, this is done with a bus interface that also receives signals from other devices controlled by the VLIW processor.
At present, an image sensing interface does not form part of a VLIW processor. This results in the necessity for an interface to be provided with the image sensor device or as an intermediate component. As a result, a bus interface of the VLIW processor is required to receive signals from this suitable interface and from other components such as memory devices. Image processing operations result in the transfer of large amounts of data. Furthermore, it is necessary to carry out a substantial amount of data processing as a result of the size of the instruction words used by the VLIW processor. This can result in an excessive demand being made of the bus interface. Further, as can be seen in the description of the prior art, it is necessary to provide at least two interfaces between the image sensor and the VLIW processor.
Applicant has filed a large number of patent applications in the field of integrated circuits and integrated circuit manufacture. As a result, the Applicant has spent much time investigating commercially viable integrated circuit devices that would be suitable for mass manufacture. As a result of the time and effort spent by the Applicant in developing this technology the Applicant has investigated the possibility of using microcontrollers to achieve low cost, yet complex image processing devices.
A microcontroller is an integrated chip that includes, on one chip, all or most of the components needed for a controller. A microcontroller is what is known as a “system on a chip.” A microcontroller can typically include the following components:
CPU (central processing unit);
RAM (Random Access Memory);
EPROM/PROM/ROM (Erasable Programmable Read Only Memory);
bus interface/s;
timers; and an
interrupt controller.
An advantage of microcontrollers is that by only including the features specific to the task (control), cost is relatively low. A typical microcontroller has bit manipulation instructions, easy and direct access to I/O (input/output) data, and quick and efficient interrupt processing. Microcontrollers are a “one-chip solution” which reduces parts count and design costs. The fact that a microcontroller is in the form of a single chip allows the manufacture of controlling devices to take place in a single integrated circuit fabrication process.
In this invention, the Applicant has conceived a microcontroller that includes a VLIW processor. In particular, the Applicant believes that a microcontroller can be provided that is specifically suited for image processing. It is submitted that this approach is generally counter-intuitive, since VLIW processors are generally used in the format shown in the drawings indicating the prior art. The reason for this is that the fabrication techniques are extremely complex. However, Applicant believes that, in the event that a sufficiently large number of microcontrollers are manufactured, the cost per unit will drop exponentially. Applicant intends utilizing the microcontroller of the present invention in a device that it is envisaged will have a high turnover. At present, it has been simply more convenient for manufacturers of image processing devices to obtain a standard VLIW processor and to program it to suit the particular application.
SUMMARY OF THE INVENTION
According to a first aspect of the invention, there is provided an image sensing and processing apparatus that comprises
an image sensor that is capable of generating signals carrying data relating to an image sensed by the image sensor; and
a microcontroller that comprises

    
    
        a wafer substrate;
        VLIW processor circuitry that is positioned on the wafer substrate;
        image sensor interface circuitry that is positioned on the wafer substrate and is connected between the VLIW processor circuitry and the image sensor, the image sensor interface circuitry being configured to facilitate communication between the VLIW processor circuitry and the image sensor; and
        bus interface circuitry that is discrete from the image sensor interface circuitry and is connected to the VLIW processor circuitry so that the VLIW processor circuitry can communicate with devices other than the image sensor via a bus.
    
    


According to a second aspect of the invention, there is provided a microcontroller for an image sensing and processing apparatus, the microcontroller comprising
a wafer substrate;
VLIW processor circuitry that is positioned on the wafer substrate;
image sensor interface circuitry that is positioned on the wafer substrate and is connected between the VLIW processor circuitry and the image sensor, the image sensor interface circuitry being configured to facilitate communication between the VLIW processor circuitry and the image sensor; and
bus interface circuitry that is discrete from the image sensor interface circuitry and is connected to the VLIW processor circuitry so that the VLIW processor circuitry can communicate with devices other than the image sensor via a bus.
The invention is now described, by way of example, with reference to the accompanying drawings. The specific nature of the following description should not be construed as limiting in any way the broad nature of this summary.



BRIEF DESCRIPTION OF THE DRAWINGS
Notwithstanding any other forms that may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:
FIG. 1 illustrates an Artcam device constructed in accordance with the preferred embodiment;
FIG. 1A illustrates a prior art image processing device that includes a CCD image sensor;
FIG. 1B illustrates a prior art image processing device that includes an APS (active pixel sensor);
FIG. 1C illustrates a prior art image processing device that includes an MPEG decoder;
FIG. 1D illustrates a schematic block diagram of an image processing device of the invention, including a CCD image sensor;
FIG. 1E illustrates a schematic block diagram of an image processing device of the invention, including an APS;
FIG. 1F includes a schematic block diagram of a digital video camera of the invention;
FIG. 2 is a schematic block diagram of the main Artcam electronic components;
FIG. 3 is a schematic block diagram of the Artcam Central Processor;
FIG. 3(a) illustrates the VLIW Vector Processor in more detail;
FIG. 4 illustrates the Processing Unit in more detail;
FIG. 5 illustrates the ALU 188 in more detail;
FIG. 6 illustrates the In block in more detail;
FIG. 7 illustrates the Out block in more detail;
FIG. 8 illustrates the Registers block in more detail;
FIG. 9 illustrates the Crossbar1 in more detail;
FIG. 10 illustrates the Crossbar2 in more detail;
FIG. 11 illustrates the read process block in more detail;
FIG. 12 illustrates the read process block in more detail;
FIG. 13 illustrates the barrel shifter block in more detail;
FIG. 14 illustrates the adder/logic block in more detail;
FIG. 15 illustrates the multiply block in more detail;
FIG. 16 illustrates the I/O address generator block in more detail;
FIG. 17 illustrates a pixel storage format;
FIG. 18 illustrates a sequential read iterator process;
FIG. 19 illustrates a box read iterator process;
FIG. 20 illustrates a box write iterator process;
FIG. 21 illustrates the vertical strip read/write iterator process;
FIG. 22 illustrates the vertical strip read/write iterator process;
FIG. 23 illustrates the generate sequential process;
FIG. 24 illustrates the generate sequential process;
FIG. 25 illustrates the generate vertical strip process;
FIG. 26 illustrates the generate vertical strip process;
FIG. 27 illustrates a pixel data configuration;
FIG. 28 illustrates a pixel processing process;
FIG. 29 illustrates a schematic block diagram of the display controller;
FIG. 30 illustrates the CCD image organization;
FIG. 31 illustrates the storage format for a logical image;
FIG. 32 illustrates the internal image memory storage format;
FIG. 33 illustrates the image pyramid storage format;
FIG. 34 illustrates the logical layout of a single printhead;
FIG. 35 illustrates the structure of the printhead interface;
FIG. 36 illustrates the process of rotation of a Lab image;
FIG. 37 illustrates the format of a pixel of the printed image;
FIG. 38 illustrates the dithering process;
FIG. 39 illustrates the process of generating an 8 bit dot output;
FIG. 40 illustrates a perspective view of the card reader;
FIG. 41 illustrates an exploded perspective of a card reader;
FIG. 42 illustrates a close up view of the Artcard reader;
FIG. 43 illustrates a perspective view of the print roll and print head;
FIG. 44 illustrates a first exploded perspective view of the print roll;
FIG. 45 illustrates a second exploded perspective view of the print roll;
FIG. 45A illustrates a three dimensional view of another embodiment of the print roll and print head in the form of a printing cartridge also in accordance with the invention;
FIG. 45B illustrates a three dimensional, sectional view of the print cartridge of FIG. 45A;
FIG. 45C shows a three dimensional, exploded view of the print cartridge of FIG. 45A;
FIG. 45D shows a three dimensional, exploded view of an ink cartridge forming part of the print cartridge of FIG. 45A;
FIG. 45E shows a three dimensional view of an air filter of the print cartridge of FIG. 45A.



DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS
The digital image processing camera system constructed in accordance with the preferred embodiment is as illustrated in FIG. 1. The camera unit 1 includes means for the insertion of an integral print roll (not shown). The camera unit 1 can include an area image sensor 2 which sensors an image 3 for captured by the camera. Optionally, the second area image sensor can be provided to also image the scene 3 and to optionally provide for the production of stereographic output effects.
The camera 1 can include an optional color display 5 for the display of the image being sensed by the sensor 2. When a simple image is being displayed on the display 5, the button 6 can be depressed resulting in the printed image 8 being output by the camera unit 1. A series of cards, herein after known as “Artcards” 9 contain, on one surface encoded information and on the other surface, contain an image distorted by the particular effect produced by the Artcard 9. The Artcard 9 is inserted in an Artcard reader 10 in the side of camera 1 and, upon insertion, results in output image 8 being distorted in the same manner as the distortion appearing on the surface of Artcard 9. Hence, by means of this simple user interface a user wishing to produce a particular effect can insert one of many Artcards 9 into the Artcard reader 10 and utilize button 19 to take a picture of the image 3 resulting in a corresponding distorted output image 8.
The camera unit 1 can also include a number of other control button 13, 14 in addition to a simple LCD output display 15 for the display of informative information including the number of printouts left on the internal print roll on the camera unit. Additionally, different output formats can be controlled by CHP switch 17.
Image Processing Apparatus 20a 
In FIG. 1D, reference numeral 20a generally indicates an image processing apparatus in accordance with the invention.
The image processing apparatus 20a includes a microcontroller 22a. The microcontroller 22a includes circuitry that defines a VLIW processor that is indicated generally at 21a. The operational details and structure of the VLIW processor is described in further detail later on in the specification.
The microcontroller also includes circuitry that defines a bus interface 23a. The bus interface permits the VLIW processor 21a to communicate with other devices indicated at 24a and with a memory, such as DRAM or EEPROM, indicated at 25a. 
The apparatus 20a includes an image sensor in the form of a CCD (charge-coupled device) sensor 26a. These sensors are widely used for image sensing. As is known, such sensors produce an analog signal upon sensing an image. It follows that it is necessary that such a signal be converted into a digital signal in order that it can be processed by the VLIW processor 21a. Further, as set out in the preamble and later on in the specification, the VLIW processor 21a makes use of long instruction words in order to process data.
Thus, the microcontroller 22a includes interface circuitry 28a that defines an interface 27a that is capable of converting a signal emanating from the image sensor 26a into a signal that can be read by the VLIW processor 21a. Further, the interface circuitry 28a defines an analog/digital converter (ADC) 29a for converting signals passing between the VLIW processor 21a and the CCD sensor 26a into an appropriate analog or digital signal.
It is important to note that the interface circuitry 28a and the VLIW processor 21a share a common wafer substrate. This provides a compact and self-contained microcontroller that is specifically suited to image processing.
In FIG. 1E, reference numeral 30a generally indicates a further image processing apparatus in accordance with the invention. With reference to FIG. 1D, like reference numerals refer to like parts, unless otherwise specified.
Instead of the CCD sensor 26a, the apparatus 30a includes a CMOS type sensor in the form of an active pixel sensor (APS) 31a. 
Such sensors generate a digital signal upon sensing an image. It follows that, in this case, the interface circuitry 28a does not include the ADC 29a. 
In FIG. 1F, reference numeral 32a generally indicates a schematic block diagram of a digital video camera, in accordance with the invention. With reference to FIGS. 1D and 1E, like reference numerals refer to like parts, unless otherwise specified.
In this example, the bus interface 23a is connected to a memory 33a and to a digital tape drive 34a. 
The camera 32a includes a CCD sensor 35a. Thus, the interface circuitry 28 includes the ADC 29a to carry out the necessary analog/digital conversion as described above. A particular advantage of the VLIW processor 21a is that it facilitates the provision of image processing, MPEG encoding, digital tape formatting and control in a single integrated circuit device that is the microcontroller 22a. 
Turning now to FIG. 2, there is illustrated a schematic view of the internal hardware of the camera unit 1. The internal hardware is based around an Artcam central processor unit (ACP) 31.
Artcam Central Processor 31
The Artcam central processor 31 provides many functions that form the ‘heart’ of the system. The ACP 31 is preferably implemented as a complex, high speed, CMOS system on-a-chip. Utilising standard cell design with some full custom regions is recommended. Fabrication on a 0.25 micron CMOS process will provide the density and speed required, along with a reasonably small die area.
The functions provided by the ACP 31 include:
1. Control and digitization of the area image sensor 2. A 3D stereoscopic version of the ACP requires two area image sensor interfaces with a second optional image sensor 4 being provided for stereoscopic effects.
2. Area image sensor compensation, reformatting, and image enhancement.
3. Memory interface and management to a memory store 33.
4. Interface, control, and analog to digital conversion of an Artcard reader linear image sensor 34 which is provided for the reading of data from the Artcards 9.
5. Extraction of the raw Artcard data from the digitized and encoded Artcard image.
6. Reed-Solomon error detection and correction of the Artcard encoded data. The encoded surface of the Artcard 9 includes information on how to process an image to produce the effects displayed on the image distorted surface of the Artcard 9. This information is in the form of a script, hereinafter known as a “Vark script”. The Vark script is utilised by an interpreter running within the ACP 31 to produce the desired effect.
7. Interpretation of the Vark script on the Artcard 9.
8. Performing image processing operations as specified by the Vark script.
9. Controlling various motors for the paper transport 36, zoom lens 38, autofocus 39 and Artcard driver 37.
10. Controlling a guillotine actuator 40 for the operation of a guillotine 41 for the cutting of photographs 8 from print roll 42.
11. Half-toning of the image data for printing.
12. Providing the print data to a print-head 44 at the appropriate times.
13. Controlling the print head 44.
14. Controlling the ink pressure feed to print-head 44.
15. Controlling optional flash unit 56.
16. Reading and acting on various sensors in the camera, including camera orientation sensor 46, autofocus 47 and Artcard insertion sensor 49.
17. Reading and acting on the user interface buttons 6, 13, 14.
18. Controlling the status display 15.
19. Providing viewfinder and preview images to the color display 5.
20. Control of the system power consumption, including the ACP power consumption via power management circuit 51.
21. Providing external communications 52 to general purpose computers (using part USB).
22. Reading and storing information in a printing roll authentication chip 53.
23. Reading and storing information in a camera authentication chip 54.
24. Communicating with an optional mini-keyboard 57 for text modification.
Quartz Crystal 58
A quartz crystal 58 is used as a frequency reference for the system clock. As the system clock is very high, the ACP 31 includes a phase locked loop clock circuit to increase the frequency derived from the crystal 58.
Image Sensing
Area Image Sensor 2
The area image sensor 2 converts an image through its lens into an electrical signal. It can either be a charge coupled device (CCD) or an active pixel sensor (APS) CMOS image sector. At present, available CCD's normally have a higher image quality, however, there is currently much development occurring in CMOS imagers. CMOS imagers are eventually expected to be substantially cheaper than CCD's have smaller pixel areas, and be able to incorporate drive circuitry and signal processing. They can also be made in CMOS fabs, which are transitioning to 12′′ wafers. CCD's are usually built in 6′′ wafer fabs, and economics may not allow a conversion to 12′′ fabs. Therefore, the difference in fabrication cost between CCD's and CMOS imagers is likely to increase, progressively favoring CMOS imagers. However, at present, a CCD is probably the best option.
The Artcam unit will produce suitable results with a 1,500×1,000 area image sensor. However, smaller sensors, such as 750×500, will be adequate for many markets. The Artcam is less sensitive to image sensor resolution than are conventional digital cameras. This is because many of the styles contained on Artcards 9 process the image in such a way as to obscure the lack of resolution. For example, if the image is distorted to simulate the effect of being converted to an impressionistic painting, low source image resolution can be used with minimal effect. Further examples for which low resolution input images will typically not be noticed include image warps which produce high distorted images, multiple miniature copies of the of the image (eg. passport photos), textural processing such as bump mapping for a base relief metal look, and photo-compositing into structured scenes.
This tolerance of low resolution image sensors may be a significant factor in reducing the manufacturing cost of an Artcam unit 1 camera. An Artcam with a low cost 750×500 image sensor will often produce superior results to a conventional digital camera with a much more expensive 1,500×1,000 image sensor.
Optional Stereoscopic 3D Image Sensor 4
The 3D versions of the Artcam unit 1 have an additional image sensor 4, for stereoscopic operation. This image sensor is identical to the main image sensor. The circuitry to drive the optional image sensor may be included as a standard part of the ACP chip 31 to reduce incremental design cost. Alternatively, a separate 3D Artcam ACP can be designed. This option will reduce the manufacturing cost of a mainstream single sensor Artcam.
Print Roll Authentication Chip 53
A small chip 53 is included in each print roll 42. This chip replaced the functions of the bar code, optical sensor and wheel, and ISO/ASA sensor on other forms of camera film units such as Advanced Photo Systems film cartridges.
The authentication chip also provides other features:
1. The storage of data rather than that which is mechanically and optically sensed from APS rolls
2. A remaining media length indication, accurate to high resolution.
3. Authentication Information to prevent inferior clone print roll copies.
The authentication chip 53 contains 1024 bits of Flash memory, of which 128 bits is an authentication key, and 512 bits is the authentication information. Also included is an encryption circuit to ensure that the authentication key cannot be accessed directly.
Print-Head 44
The Artcam unit 1 can utilize any color print technology which is small enough, low enough power, fast enough, high enough quality, and low enough cost, and is compatible with the print roll. Relevant printheads will be specifically discussed hereinafter.
The specifications of the ink jet head are:
















Image type
Bi-level, dithered



Color
CMY Process Color



Resolution
1600 dpi



Print head length
‘Page-width’ (100 mm)



Print speed
2 seconds per photo










Optional Ink Pressure Controller (not Shown)

The function of the ink pressure controller depends upon the type of ink jet print head 44 incorporated in the Artcam. For some types of ink jet, the use of an ink pressure controller can be eliminated, as the ink pressure is simply atmospheric pressure. Other types of print head require a regulated positive ink pressure. In this case, the in pressure controller consists of a pump and pressure transducer.
Other print heads may require an ultrasonic transducer to cause regular oscillations in the ink pressure, typically at frequencies around 100 KHz. In the case, the ACP 31 controls the frequency phase and amplitude of these oscillations.
Paper Transport Motor 36
The paper transport motor 36 moves the paper from within the print roll 42 past the print head at a relatively constant rate. The motor 36 is a miniature motor geared down to an appropriate speed to drive rollers which move the paper. A high quality motor and mechanical gears are required to achieve high image quality, as mechanical rumble or other vibrations will affect the printed dot row spacing.
Paper Transport Motor Driver 60
The motor driver 60 is a small circuit which amplifies the digital motor control signals from the APC 31 to levels suitable for driving the motor 36.
Paper Pull Sensor
A paper pull sensor 50 detects a user's attempt to pull a photo from the camera unit during the printing process. The APC 31 reads this sensor 50, and activates the guillotine 41 if the condition occurs. The paper pull sensor 50 is incorporated to make the camera more ‘foolproof’ in operation. Were the user to pull the paper out forcefully during printing, the print mechanism 44 or print roll 42 may (in extreme cases) be damaged. Since it is acceptable to pull out the ‘pod’ from a Polaroid type camera before it is fully ejected, the public has been ‘trained’ to do this. Therefore, they are unlikely to heed printed instructions not to pull the paper.
The Artcam preferably restarts the photo print process after the guillotine 41 has cut the paper after pull sensing.
The pull sensor can be implemented as a strain gauge sensor, or as an optical sensor detecting a small plastic flag which is deflected by the torque that occurs on the paper drive rollers when the paper is pulled. The latter implementation is recommendation for low cost.
Paper Guillotine Actuator 40
The paper guillotine actuator 40 is a small actuator which causes the guillotine 41 to cut the paper either at the end of a photograph, or when the paper pull sensor 50 is activated.
The guillotine actuator 40 is a small circuit which amplifies a guillotine control signal from the APC tot the level required by the actuator 41.
Artcard 9
The Artcard 9 is a program storage medium for the Artcam unit. As noted previously, the programs are in the form of Vark scripts. Vark is a powerful image processing language especially developed for the Artcam unit. Each Artcard 9 contains one Vark script, and thereby defines one image processing style.
Preferably, the VARK language is highly image processing specific. By being highly image processing specific, the amount of storage required to store the details on the card are substantially reduced. Further, the ease with which new programs can be created, including enhanced effects, is also substantially increased. Preferably, the language includes facilities for handling many image processing functions including image warping via a warp map, convolution, color lookup tables, posterizing an image, adding noise to an image, image enhancement filters, painting algorithms, brush jittering and manipulation edge detection filters, tiling, illumination via light sources, bump maps, text, face detection and object detection attributes, fonts, including three dimensional fonts, and arbitrary complexity pre-rendered icons. Further details of the operation of the Vark language interpreter are contained hereinafter.
Hence, by utilizing the language constructs as defined by the created language, new affects on arbitrary images can be created and constructed for inexpensive storage on Artcard and subsequent distribution to camera owners. Further, on one surface of the card can be provided an example illustrating the effect that a particular VARK script, stored on the other surface of the card, will have on an arbitrary captured image.
By utilizing such a system, camera technology can be distributed without a great fear of obsolescence in that, provided a VARK interpreter is incorporated in the camera device, a device independent scenario is provided whereby the underlying technology can be completely varied over time. Further, the VARK scripts can be updated as new filters are created and distributed in an inexpensive manner, such as via simple cards for card reading.
The Artcard 9 is a piece of thin white plastic with the same format as a credit card (86 mm long by 54 mm wide). The Artcard is printed on both sides using a high resolution ink jet printer. The inkjet printer technology is assumed to be the same as that used in the Artcam, with 1600 dpi (63 dpmm) resolution. A major feature of the Artcard 9 is low manufacturing cost. Artcards can be manufactured at high speeds as a wide web of plastic film. The plastic web is coated on both sides with a hydrophilic dye fixing layer. The web is printed simultaneously on both sides using a ‘pagewidth’ color ink jet printer. The web is then cut and punched into individual cards. On one face of the card is printed a human readable representation of the effect the Artcard 9 will have on the sensed image. This can be simply a standard image which has been processed using the Vark script stored on the back face of the card.
On the back face of the card is printed an array of dots which can be decoded into the Vark script that defines the image processing sequence. The print area is 80 mm×50 mm, giving a total of 15,876,000 dots. This array of dots could represent at least 1.89 Mbytes of data. To achieve high reliability, extensive error detection and correction is incorporated in the array of dots. This allows a substantial portion of the card to be defaced, worn, creased, or dirty with no effect on data integrity. The data coding used is Reed-Solomon coding, with half of the data devoted to error correction. This allows the storage of 967 Kbytes of error corrected data on each Artcard 9.
Linear Image Sensor 34
The Artcard linear sensor 34 converts the aforementioned Artcard data image to electrical signals. As with the area image sensor 2, 4, the linear image sensor can be fabricated using either CCD or APS CMOS technology. The active length of the image sensor 34 is 50 mm, equal to the width of the data array on the Artcard 9. To satisfy Nyquist's sampling theorem, the resolution of the linear image sensor 34 must be at least twice the highest spatial frequency of the Artcard optical image reaching the image sensor. In practice, data detection is easier if the image sensor resolution is substantially above this. A resolution of 4800 dpi (189 dpmm) is chosen, giving a total of 9,450 pixels. This resolution requires a pixel sensor pitch of 5.3 μm. This can readily be achieved by using four staggered rows of 20 μm pixel sensors.
The linear image sensor is mounted in a special package which includes a LED 65 to illuminate the Artcard 9 via a light-pipe (not shown).
The Artcard reader light-pipe can be a molded light-pipe which has several function:
1. It diffuses the light from the LED over the width of the card using total internal reflection facets.
2. It focuses the light onto a 16 μm wide strip of the Artcard 9 using an integrated cylindrical lens.
3. It focuses light reflected from the Artcard onto the linear image sensor pixels using a molded array of microlenses.
The operation of the Artcard reader is explained further hereinafter.
Artcard Reader Motor 37
The Artcard reader motor propels the Artcard past the linear image sensor 34 at a relatively constant rate. As it may not be cost effective to include extreme precision mechanical components in the Artcard reader, the motor 37 is a standard miniature motor geared down to an appropriate speed to drive a pair of rollers which move the Artcard 9. The speed variations, rumble, and other vibrations will affect the raw image data as circuitry within the APC 31 includes extensive compensation for these effects to reliably read the Artcard data.
The motor 37 is driven in reverse when the Artcard is to be ejected.
Artcard Motor Driver 61
The Artcard motor driver 61 is a small circuit which amplifies the digital motor control signals from the APC 31 to levels suitable for driving the motor 37.
Card Insertion Sensor 49
The card insertion sensor 49 is an optical sensor which detects the presence of a card as it is being inserted in the card reader 34. Upon a signal from this sensor 49, the APC 31 initiates the card reading process, including the activation of the Artcard reader motor 37.
Card Eject Button 16
A card eject button 16 (FIG. 1) is used by the user to eject the current Artcard, so that another Artcard can be inserted. The APC 31 detects the pressing of the button, and reverses the Artcard reader motor 37 to eject the card.
Card Status Indicator 66
A card status indicator 66 is provided to signal the user as to the status of the Artcard reading process. This can be a standard bi-color (red/green) LED. When the card is successfully read, and data integrity has been verified, the LED lights up green continually. If the card is faulty, then the LED lights up red.
If the camera is powered from a 1.5 V instead of 3V battery, then the power supply voltage is less than the forward voltage drop of the greed LED, and the LED will not light. In this case, red LEDs can be used, or the LED can be powered from a voltage pump which also powers other circuits in the Artcam which require higher voltage.
64 Mbit DRAM 33
To perform the wide variety of image processing effects, the camera utilizes 8 Mbytes of memory 33. This can be provided by a single 64 Mbit memory chip. Of course, with changing memory technology increased Dram storage sizes may be substituted.
High speed access to the memory chip is required. This can be achieved by using a Rambus DRAM (burst access rate of 500 Mbytes per second) or chips using the new open standards such as double data rate (DDR) SDRAM or Synclink DRAM.
Camera Authentication Chip
The camera authentication chip 54 is identical to the print roll authentication chip 53, except that it has different information stored in it. The camera authentication chip 54 has three main purposes:
1. To provide a secure means of comparing authentication codes with the print roll authentication chip;
2. To provide storage for manufacturing information, such as the serial number of the camera;
3. To provide a small amount of non-volatile memory for storage of user information.
Displays
The Artcam includes an optional color display 5 and small status display 15. Lowest cost consumer cameras may include a color image display, such as a small TFT LCD 5 similar to those found on some digital cameras and camcorders. The color display 5 is a major cost element of these versions of Artcam, and the display 5 plus back light are a major power consumption drain.
Status Display 15
The status display 15 is a small passive segment based LCD, similar to those currently provided on silver halide and digital cameras. Its main function is to show the number of prints remaining in the print roll 42 and icons for various standard camera features, such as flash and battery status.
Color Display 5
The color display 5 is a full motion image display which operates as a viewfinder, as a verification of the image to be printed, and as a user interface display. The cost of the display 5 is approximately proportional to its area, so large displays (say 4′′ diagonal) unit will be restricted to expensive versions of the Artcam unit. Smaller displays, such as color camcorder viewfinder TFT's at around 1′′, may be effective for mid-range Artcams.
Zoom Lens (not Shown)
The Artcam can include a zoom lens. This can be a standard electronically controlled zoom lens, identical to one which would be used on a standard electronic camera, and similar to pocket camera zoom lenses. A referred version of the Artcam unit may include standard interchangeable 35 mm SLR lenses.
Autofocus Motor 39
The autofocus motor 39 changes the focus of the zoom lens. The motor is a miniature motor geared down to an appropriate speed to drive the autofocus mechanism.
Autofocus Motor Driver 63
The autofocus motor driver 63 is a small circuit which amplifies the digital motor control signals from the APC 31 to levels suitable for driving the motor 39.
Zoom Motor 38
The zoom motor 38 moves the zoom front lenses in and out. The motor is a miniature motor geared down to an appropriate speed to drive the zoom mechanism.
Zoom Motor Driver 62
The zoom motor driver 62 is a small circuit which amplifies the digital motor control signals from the APC 31 to levels suitable for driving the motor.
Communications
The ACP 31 contains a universal serial bus (USB) interface 52 for communication with personal computers. Not all Artcam models are intended to include the USB connector. However, the silicon area required for a USB circuit 52 is small, so the interface can be included in the standard ACP.
Optional Keyboard 57
The Artcam unit may include an optional miniature keyboard 57 for customizing text specified by the Artcard. Any text appearing in an Artcard image may be editable, even if it is in a complex metallic 3D font. The miniature keyboard includes a single line alphanumeric LCD to display the original text and edited text. The keyboard may be a standard accessory.
The ACP 31 contains a serial communications circuit for transferring data to and from the miniature keyboard.
Power Supply
The Artcam unit uses a battery 48. Depending upon the Artcam options, this is either a 3V Lithium cell, 1.5 V AA alkaline cells, or other battery arrangement.
Power Management Unit 51
Power consumption is an important design constraint in the Artcam. It is desirable that either standard camera batteries (such as 3V lithium batters) or standard AA or AAA alkaline cells can be used. While the electronic complexity of the Artcam unit is dramatically higher than 35 mm photographic cameras, the power consumption need not be commensurately higher. Power in the Artcam can be carefully managed with all units being turned off when not in use.
The most significant current drains are the ACP 31, the area image sensors 2,4, the printer 44 various motors, the flash unit 56, and the optional color display 5 dealing with each part separately:
1. ACP: If fabricated using 0.25 μm CMOS, and running on 1.5V, the ACP power consumption can be quite low. Clocks to various parts of the ACP chip can be quite low. Clocks to various parts of the ACP chip can be turned off when not in use, virtually eliminating standby current consumption. The ACP will only fully used for approximately 4 seconds for each photograph printed.
2. Area image sensor: power is only supplied to the area image sensor when the user has their finger on the button.
3. The printer power is only supplied to the printer when actually printing. This is for around 2 seconds for each photograph. Even so, suitably lower power consumption printing should be used.
4. The motors required in the Artcam are all low power miniature motors, and are typically only activated for a few seconds per photo.
5. The flash unit 45 is only used for some photographs. Its power consumption can readily be provided by a 3V lithium battery for a reasonably battery life.
6. The optional color display 5 is a major current drain for two reasons: it must be on for the whole time that the camera is in use, and a backlight will be required if a liquid crystal display is used. Cameras that incorporate a color display will require a larger battery to achieve acceptable batter life.
Flash Unit 56
The flash unit 56 can be a standard miniature electronic flash for consumer cameras.
Overview of the ACP 31
FIG. 3 illustrates the Artcam Central Processor (ACP) 31 in more detail. The Artcam Central Processor provides all of the processing power for Artcam. It is designed for a 0.25 micron CMOS process, with approximately 1.5 million transistors and an area of around 50 mm2. The ACP 31 is a complex design, but design effort can be reduced by the use of datapath compilation techniques, macrocells, and IP cores. The ACP 31 contains:

    
    
        A RISC CPU core 72
        A 4 way parallel VLIW Vector Processor 74
        A Direct RAMbus interface 81
        A CMOS image sensor interface 83
        A CMOS linear image sensor interface 88
        A USB serial interface 52
        An infrared keyboard interface 55
        A numeric LCD interface 84, and
        A color TFT LCD interface 88
        A 4 Mbyte Flash memory 70 for program storage 70
    
    


The RISC CPU, Direct RAMbus interface 81, CMOS sensor interface 83 and USB serial interface 52 can be vendor supplied cores. The ACP 31 is intended to run at a clock speed of 200 MHz on 3V externally and 1.5V internally to minimize power consumption. The CPU core needs only to run at 100 MHz. The following two block diagrams give two views of the ACP 31:

    
    
        A view of the ACP 31 in isolation

An example Artcam showing a high-level view of the ACP 31 connected to the rest of the Artcam hardware.

Image Access

    
    


As stated previously, the DRAM Interface 81 is responsible for interfacing between other client portions of the ACP chip and the RAMBUS DRAM. In effect, each module within the DRAM Interface is an address generator.
There are three logical types of images manipulated by the ACP. They are:

    
    
        CCD Image, which is the Input Image captured from the CCD.
        Internal Image format—the Image format utilised internally by the Artcam device.
    
    


Print Image—the Output Image format printed by the Artcam
These images are typically different in color space, resolution, and the output & input color spaces which can vary from camera to camera. For example, a CCD image on a low-end camera may be a different resolution, or have different color characteristics from that used in a high-end camera. However all internal image formats are the same format in terms of color space across all cameras.
In addition, the three image types can vary with respect to which direction is ‘up’. The physical orientation of the camera causes the notion of a portrait or landscape image, and this must be maintained throughout processing. For this reason, the internal image is always oriented correctly, and rotation is performed on images obtained from the CCD and during the print operation.
CPU Core (CPU) 72
The ACP 31 incorporates a 32 bit RISC CPU 72 to run the Vark image processing language interpreter and to perform Artcam's general operating system duties. A wide variety of CPU cores are suitable: it can be any processor core with sufficient processing power to perform the required core calculations and control functions fast enough to met consumer expectations. Examples of suitable cores are: MIPS R4000 core from LSI Logic, StrongARM core. There is no need to maintain instruction set continuity between different Artcam models. Artcard compatibility is maintained irrespective of future processor advances and changes, because the Vark interpreter is simply re-compiled for each new instruction set. The ACP 31 architecture is therefore also free to evolve. Different ACP 31 chip designs may be fabricated by different manufacturers, without requiring to license or port the CPU core. This device independence avoids the chip vendor lock-in such as has occurred in the PC market with Intel. The CPU operates at 100 MHz, with a single cycle time of 10 ns. It must be fast enough to run the Vark interpreter, although the VLIW Vector Processor 74 is responsible for most of the time-critical operations.
Program Cache 72
Although the program code is stored in on-chip Flash memory 70, it is unlikely that well packed Flash memory 70 will be able to operate at the 10 ns cycle time required by the CPU. Consequently a small cache is required for good performance. 16 cache lines of 32 bytes each are sufficient, for a total of 512 bytes. The program cache 72 is defined in the chapter entitled Program cache 72.
Data Cache 76
A small data cache 76 is required for good performance. This requirement is mostly due to the use of a RAMbus DRAM, which can provide high-speed data in bursts, but is inefficient for single byte accesses. The CPU has access to a memory caching system that allows flexible manipulation of CPU data cache 76 sizes. A minimum of 16 cache lines (512 bytes) is recommended for good performance.
CPU Memory Model
An Artcam's CPU memory model consists of a 32 MB area. It consists of 8 MB of physical RDRAM off-chip in the base model of Artcam, with provision for up to 16 MB of off-chip memory. There is a 4 MB Flash memory 70 on the ACP 31 for program storage, and finally a 4 MB address space mapped to the various registers and controls of the ACP 31. The memory map then, for an Artcam is as follows:














Contents
Size









Base Artcam DRAM
8 MB



Extended DRAM
8 MB



Program memory (on ACP 31 in Flash memory 70)
4 MB



Reserved for extension of program memory
4 MB



ACP 31 registers and memory-mapped I/O
4 MB



Reserved
4 MB



TOTAL
32 MB 










A straightforward way of decoding addresses is to use address bits 23-24:

    
    
        If bit 24 is clear, the address is in the lower 16-MB range, and hence can be satisfied from DRAM and the Data cache 76. In most cases the DRAM will only be 8 MB, but 16 MB is allocated to cater for a higher memory model Artcams.
        If bit 24 is set, and bit 23 is clear, then the address represents the Flash memory 70 4 Mbyte range and is satisfied by the Program cache 72.
        If bit 24=1 and bit 23=1, the address is translated into an access over the low speed bus to the requested component in the AC by the CPU Memory Decoder 68.

Flash Memory 70

    
    


The ACP 31 contains a 4 Mbyte Flash memory 70 for storing the Artcam program. It is envisaged that Flash memory 70 will have denser packing coefficients than masked ROM, and allows for greater flexibility for testing camera program code. The downside of the Flash memory 70 is the access time, which is unlikely to be fast enough for the 100 MHz operating speed (10 ns cycle time) of the CPU. A fast Program Instruction cache 77 therefore acts as the interface between the CPU and the slower Flash memory 70.
Program Cache 72
A small cache is required for good CPU performance. This requirement is due to the slow speed Flash memory 70 which stores the Program code. 16 cache lines of 32 bytes each are sufficient, for a total of 512 bytes. The Program cache 72 is a read only cache. The data used by CPU programs comes through the CPU Memory Decoder 68 and if the address is in DRAM, through the general Data cache 76. The separation allows the CPU to operate independently of the VLIW Vector Processor 74. If the data requirements are low for a given process, it can consequently operate completely out of cache.
Finally, the Program cache 72 can be read as data by the CPU rather than purely as program instructions. This allows tables, microcode for the VLIW etc to be loaded from the Flash memory 70. Addresses with bit 24 set and bit 23 clear are satisfied from the Program cache 72.
CPU Memory Decoder 68
The CPU Memory Decoder 68 is a simple decoder for satisfying CPU data accesses. The Decoder translates data addresses into internal ACP register accesses over the internal low speed bus, and therefore allows for memory mapped I/O of ACP registers. The CPU Memory Decoder 68 only interprets addresses that have bit 24 set and bit 23 clear. There is no caching in the CPU Memory Decoder 68.
DRAM Interface 81
The DRAM used by the Artcam is a single channel 64 Mbit (8 MB) RAMbus RDRAM operating at 1.6 GB/sec. RDRAM accesses are by a single channel (16-bit data path) controller. The RDRAM also has several useful operating modes for low power operation. Although the Rambus specification describes a system with random 32 byte transfers as capable of achieving a greater than 95% efficiency, this is not true if only part of the 32 bytes are used. Two reads followed by two writes to the same device yields over 86% efficiency. The primary latency is required for bus turn-around going from a Write to a Read, and since there is a Delayed Write mechanism, efficiency can be further improved. With regards to writes, Write Masks allow specific subsets of bytes to be written to. These write masks would be set via internal cache “dirty bits”. The upshot of the Rambus Direct RDRAM is a throughput of >1 GB/sec is easily achievable, and with multiple reads for every write (most processes) combined with intelligent algorithms making good use of 32 byte transfer knowledge, transfer rates of >1.3 GB/sec are expected. Every 10 ns, 16 bytes can be transferred to or from the core.
DRAM Organization
The DRAM organization for a base model (8 MB RDRAM) Artcam is as follows:














Contents
Size









Program scratch RAM
0.50 MB



Artcard data
1.00 MB



Photo Image, captured from CMOS Sensor
0.50 MB



Print Image (compressed)
2.25 MB



1 Channel of expanded Photo Image
1.50 MB



1 Image Pyramid of single channel
1.00 MB



Intermediate Image Processing
1.25 MB



TOTAL
  8 MB







Notes:



Uncompressed, the Print Image requires 4.5 MB (1.5 MB per channel). To accommodate other objects in the 8 MB model, the Print Image needs to be compressed. If the chrominance channels are compressed by 4:1 they require only 0.375 MB each).



The memory model described here assumes a single 8 MB RDRAM. Other models of the Artcam may have more memory, and thus not require compression of the Print Image. In addition, with more memory a larger part of the final image can be worked on at once, potentially giving a speed improvement.



Note that ejecting or inserting an Artcard invalidates the 5.5 MB area holding the Print Image, 1 channel of expanded photo image, and the image pyramid. This space may be safely used by the Artcard Interface for decoding the Artcard data.






Data Cache 76

The ACP 31 contains a dedicated CPU instruction cache 77 and a general data cache 76. The Data cache 76 handles all DRAM requests (reads and writes of data) from the CPU, the VLIW Vector Processor 74, and the Display Controller 88. These requests may have very different profiles in terms of memory usage and algorithmic timing requirements. For example, a VLIW process may be processing an image in linear memory, and lookup a value in a table for each value in the image. There is little need to cache much of the image, but it may be desirable to cache the entire lookup table so that no real memory access is required. Because of these differing requirements, the Data cache 76 allows for an intelligent definition of caching. Although the Rambus DRAM interface 81 is capable of very high-speed memory access (an average throughput of 32 bytes in 25 ns), it is not efficient dealing with single byte requests. In order to reduce effective memory latency, the ACP 31 contains 128 cache lines. Each cache line is 32 bytes wide. Thus the total amount of data cache 76 is 4096 bytes (4 KB). The 128 cache lines are configured into 16 programmable-sized groups. Each of the 16 groups must be a contiguous set of cache lines. The CPU is responsible for determining how many cache lines to allocate to each group. Within each group cache lines are filled according to a simple Least Recently Used algorithm. In terms of CPU data requests, the Data cache 76 handles memory access requests that have address bit 24 clear. If bit 24 is clear, the address is in the lower 16 MB range, and hence can be satisfied from DRAM and the Data cache 76. In most cases the DRAM will only be 8 MB, but 16 MB is allocated to cater for a higher memory model Artcam. If bit 24 is set, the address is ignored by the Data cache 76.
All CPU data requests are satisfied from Cache Group 0. A minimum of 16 cache lines is recommended for good CPU performance, although the CPU can assign any number of cache lines (except none) to Cache Group 0. The remaining Cache Groups (1 to 15) are allocated according to the current requirements. This could mean allocation to a VLIW Vector Processor 74 program or the Display Controller 88. For example, a 256 byte lookup table required to be permanently available would require 8 cache lines. Writing out a sequential image would only require 2-4 cache lines (depending on the size of record being generated and whether write requests are being Write Delayed for a significant number of cycles). Associated with each cache line byte is a dirty bit, used for creating a Write Mask when writing memory to DRAM. Associated with each cache line is another dirty bit, which indicates whether any of the cache line bytes has been written to (and therefore the cache line must be written back to DRAM before it can be reused). Note that it is possible for two different Cache Groups to be accessing the same address in memory and to get out of sync. The VLIW program writer is responsible to ensure that this is not an issue. It could be perfectly reasonable, for example, to have a Cache Group responsible for reading an image, and another Cache Group responsible for writing the changed image back to memory again. If the images are read or written sequentially there may be advantages in allocating cache lines in this manner. A total of 8 buses 182 connect the VLIW Vector Processor 74 to the Data cache 76. Each bus is connected to an I/O Address Generator. (There are 2 I/O Address Generators 189, 190 per Processing Unit 178, and there are 4 Processing Units in the VLIW Vector Processor 74. The total number of buses is therefore 8.)
In any given cycle, in addition to a single 32 bit (4 byte) access to the CPU's cache group (Group 0), 4 simultaneous accesses of 16 bits (2 bytes) to remaining cache groups are permitted on the 8 VLIW Vector Processor 74 buses. The Data cache 76 is responsible for fairly processing the requests. On a given cycle, no more than 1 request to a specific Cache Group will be processed. Given that there are 8 Address Generators 189, 190 in the VLIW Vector Processor 74, each one of these has the potential to refer to an individual Cache Group. However it is possible and occasionally reasonable for 2 or more Address Generators 189, 190 to access the same Cache Group. The CPU is responsible for ensuring that the Cache Groups have been allocated the correct number of cache lines, and that the various Address Generators 189, 190 in the VLIW Vector Processor 74 reference the specific Cache Groups correctly. The Data cache 76 as described allows for the Display Controller 88 and VLIW Vector Processor 74 to be active simultaneously. If the operation of these two components were deemed to never occur simultaneously, a total 9 Cache Groups would suffice. The CPU would use Cache Group 0, and the VLIW Vector Processor 74 and the Display Controller 88 would share the remaining 8 Cache Groups, requiring only 3 bits (rather than 4) to define which Cache Group would satisfy a particular request.
JTAG Interface 85
A standard JTAG (Joint Test Action Group) Interface is included in the ACP 31 for testing purposes. Due to the complexity of the chip, a variety of testing techniques are required, including BIST (Built In Self Test) and functional block isolation. An overhead of 10% in chip area is assumed for overall chip testing circuitry. The test circuitry is beyond the scope of this document.
Serial Interfaces
USB Serial Port Interface 52
This is a standard USB serial port, which is connected to the internal chip low speed bus, thereby allowing the CPU to control it.
Keyboard Interface 65
This is a standard low-speed serial port, which is connected to the internal chip low speed bus, thereby allowing the CPU to control it. It is designed to be optionally connected to a keyboard to allow simple data input to customize prints.
Authentication Chip Serial Interfaces 64
These are 2 standard low-speed serial ports, which are connected to the internal chip low speed bus, thereby allowing the CPU to control them. The reason for having 2 ports is to connect to both the on-camera Authentication chip, and to the print-roll Authentication chip using separate lines. Only using 1 line may make it possible for a clone print-roll manufacturer to design a chip which, instead of generating an authentication code, tricks the camera into using the code generated by the authentication chip in the camera.
Parallel Interface 67
The parallel interface connects the ACP 31 to individual static electrical signals. The CPU is able to control each of these connections as memory-mapped I/O via the low speed bus The following table is a list of connections to the parallel interface:















Connection
Direction
Pins




















Paper transport stepper motor
Out
4



Artcard stepper motor
Out
4



Zoom stepper motor
Out
4



Guillotine motor
Out
1



Flash trigger
Out
1



Status LCD segment drivers
Out
7



Status LCD common drivers
Out
4



Artcard illumination LED
Out
1



Artcard status LED (red/green)
In
2



Artcard sensor
In
1



Paper pull sensor
In
1



Orientation sensor
In
2



Buttons
In
4




TOTAL
36










VLIW Input and Output FIFOs 78, 79

The VLIW Input and Output FIFOs are 8 bit wide FIFOs used for communicating between processes and the VLIW Vector Processor 74. Both FIFOs are under the control of the VLIW Vector Processor 74, but can be cleared and queried (e.g. for status) etc by the CPU.
VLIW Input FIFO 78
A client writes 8-bit data to the VLIW Input FIFO 78 in order to have the data processed by the VLIW Vector Processor 74. Clients include the Image Sensor Interface, Artcard Interface, and CPU. Each of these processes is able to offload processing by simply writing the data to the FIFO, and letting the VLIW Vector Processor 74 do all the hard work. An example of the use of a client's use of the VLIW Input FIFO 78 is the Image Sensor Interface (ISI 83). The ISI 83 takes data from the Image Sensor and writes it to the FIFO. A VLIW process takes it from the FIFO, transforming it into the correct image data format, and writing it out to DRAM. The ISI 83 becomes much simpler as a result.
VLIW Output FIFO 79
The VLIW Vector Processor 74 writes 8-bit data to the VLIW Output FIFO 79 where clients can read it. Clients include the Print Head Interface and the CPU. Both of these clients is able to offload processing by simply reading the already processed data from the FIFO, and letting the VLIW Vector Processor 74 do all the hard work. The CPU can also be interrupted whenever data is placed into the VLIW Output FIFO 79, allowing it to only process the data as it becomes available rather than polling the FIFO continuously. An example of the use of a client's use of the VLIW Output FIFO 79 is the Print Head Interface (PHI 62). A VLIW process takes an image, rotates it to the correct orientation, color converts it, and dithers the resulting image according to the print head requirements. The PHI 62 reads the dithered formatted 8-bit data from the VLIW Output FIFO 79 and simply passes it on to the Print Head external to the ACP 31. The PHI 62 becomes much simpler as a result.
VLIW Vector Processor 74
To achieve the high processing requirements of Artcam, the ACP 31 contains a VLIW (Very Long Instruction Word) Vector Processor. The VLIW processor is a set of 4 identical Processing Units (PU e.g 178) working in parallel, connected by a crossbar switch 183. Each PU e.g 178 can perform four 8-bit multiplications, eight 8-bit additions, three 32-bit additions, I/O processing, and various logical operations in each cycle. The PUs e.g 178 are microcoded, and each has two Address Generators 189, 190 to allow full use of available cycles for data processing. The four PUs e.g 178 are normally synchronized to provide a tightly interacting VLIW processor. Clocking at 200 MHz, the VLIW Vector Processor 74 runs at 12 Gops (12 billion operations per second). Instructions are tuned for image processing functions such as warping, artistic brushing, complex synthetic illumination, color transforms, image filtering, and compositing. These are accelerated by two orders of magnitude over desktop computers. As shown in more detail in FIG. 3(a), the VLIW Vector Processor 74 is 4 PUs e.g 178 connected by a crossbar switch 183 such that each PU e.g 178 provides two inputs to, and takes two outputs from, the crossbar switch 183. Two common registers form a control and synchronization mechanism for the PUs e.g 178. 8 Cache buses 182 allow connectivity to DRAM via the Data cache 76, with 2 buses going to each PU e.g 178 (1 bus per I/O Address Generator).
Each PU e.g 178 consists of an ALU 188 (containing a number of registers & some arithmetic logic for processing data), some microcode RAM 196, and connections to the outside world (including other ALUs). A local PU state machine runs in microcode and is the means by which the PU e.g 178 is controlled. Each PU e.g 178 contains two I/O Address Generators 189, 190 controlling data flow between DRAM (via the Data cache 76) and the ALU 188 (via Input FIFO and Output FIFO). The address generator is able to read and write data (specifically images in a variety of formats) as well as tables and simulated FIFOs in DRAM. The formats are customizable under software control, but are not microcoded. Data taken from the Data cache 76 is transferred to the ALU 188 via the 16-bit wide Input FIFO. Output data is written to the 16-bit wide Output FIFO and from there to the Data cache 76. Finally, all PUs e.g 178 share a single 8-bit wide VLIW Input FIFO 78 and a single 8-bit wide VLIW Output FIFO 79. The low speed data bus connection allows the CPU to read and write registers in the PU e.g 178, update microcode, as well as the common registers shared by all PUs e.g 178 in the VLIW Vector Processor 74. Turning now to FIG. 4, a closer detail of the internals of a single PU e.g 178 can be seen, with components and control signals detailed in subsequent hereinafter:
Microcode
Each PU e.g 178 contains a microcode RAM 196 to hold the program for that particular PU e.g 178. Rather than have the microcode in ROM, the microcode is in RAM, with the CPU responsible for loading it up. For the same space on chip, this tradeoff reduces the maximum size of any one function to the size of the RAM, but allows an unlimited number of functions to be written in microcode. Functions implemented using microcode include Vark acceleration, Artcard reading, and Printing. The VLIW Vector Processor 74 scheme has several advantages for the case of the ACP 31:

    
    
        Hardware design complexity is reduced
        Hardware risk is reduced due to reduction in complexity
        Hardware design time does not depend on all Vark functionality being implemented in dedicated silicon
        Space on chip is reduced overall (due to large number of processes able to be implemented as microcode)
        Functionality can be added to Vark (via microcode) with no impact on hardware design time
    
    


Size and Content
The CPU loaded microcode RAM 196 for controlling each PU e.g 178 is 128 words, with each word being 96 bits wide. A summary of the microcode size for control of various units of the PU e.g 178 is listed in the following table:














Process Block
Size (bits)



















Status Output
3



Branching (microcode control)
11



In
8



Out
6



Registers
7



Read
10



Write
6



Barrel Shifter
12



Adder/Logical
14



Multiply/Interpolate
19



TOTAL
96










With 128 instruction words, the total microcode RAM 196 per PU e.g 178 is 12,288 bits, or 1.5 KB exactly. Since the VLIW Vector Processor 74 consists of 4 identical PUs e.g 178 this equates to 6,144 bytes, exactly 6 KB. Some of the bits in a microcode word are directly used as control bits, while others are decoded. See the various unit descriptions that detail the interpretation of each of the bits of the microcode word.
Synchronization Between PUs e.g 178
Each PU e.g 178 contains a 4 bit Synchronization Register 197. It is a mask used to determine which PUs e.g 178 work together, and has one bit set for each of the corresponding PUs e.g 178 that are functioning as a single process. For example, if all of the PUs e.g 178 were functioning as a single process, each of the 4 Synchronization Register 197s would have all 4 bits set. If there were two asynchronous processes of 2 PUs e.g 178 each, two of the PUs e.g 178 would have 2 bits set in their Synchronization Register 197s (corresponding to themselves), and the other two would have the other 2 bits set in their Synchronization Register 197s (corresponding to themselves).
The Synchronization Register 197 is used in two basic ways:

    
    
        Stopping and starting a given process in synchrony
        Suspending execution within a process

Stopping and Starting Processes

    
    


The CPU is responsible for loading the microcode RAM 196 and loading the execution address for the first instruction (usually 0). When the CPU starts executing microcode, it begins at the specified address.
Execution of microcode only occurs when all the bits of the Synchronization Register 197 are also set in the Common Synchronization Register 197. The CPU therefore sets up all the PUs e.g 178 and then starts or stops processes with a single write to the Common Synchronization Register 197.
This synchronization scheme allows multiple processes to be running asynchronously on the PUs e.g 178, being stopped and started as processes rather than one PU e.g 178 at a time.
Suspending Execution within a Process
In a given cycle, a PU e.g 178 may need to read from or write to a FIFO (based on the opcode of the current microcode instruction). If the FIFO is empty on a read request, or full on a write request, the FIFO request cannot be completed. The PU e.g 178 will therefore assert its SuspendProcess control signal 198. The SuspendProcess signals from all PUs e.g 178 are fed back to all the PUs e.g 178. The Synchronization Register 197 is ANDed with the 4 SuspendProcess bits, and if the result is non-zero, none of the PU e.g 178's register WriteEnables or FIFO strobes will be set. Consequently none of the PUs e.g 178 that form the same process group as the PU e.g 178 that was unable to complete its task will have their registers or FIFOs updated during that cycle. This simple technique keeps a given process group in synchronization. Each subsequent cycle the PU e.g 178's state machine will attempt to re-execute the microcode instruction at the same address, and will continue to do so until successful. Of course the Common Synchronization Register 197 can be written to by the CPU to stop the entire process if necessary. This synchronization scheme allows any combinations of PUs e.g 178 to work together, each group only affecting its co-workers with regards to suspension due to data not being ready for reading or writing.
Control and Branching
During each cycle, each of the four basic input and calculation units within a PU e.g 178's ALU 188 (Read, Adder/Logic, Multiply/Interpolate, and Barrel Shifter) produces two status bits: a Zero flag and a Negative flag indicating whether the result of the operation during that cycle was 0 or negative. Each cycle one of those 4 status bits is chosen by microcode instructions to be output from the PU e.g 178. The 4 status bits (1 per PU e.g 178's ALU 188) are combined into a 4 bit Common Status Register 200. During the next cycle, each PU e.g 178's microcode program can select one of the bits from the Common Status Register 200, and branch to another microcode address dependant on the value of the status bit.
Status Bit
Each PU e.g 178's ALU 188 contains a number of input and calculation units. Each unit produces 2 status bits—a negative flag and a zero flag. One of these status bits is output from the PU e.g 178 when a particular unit asserts the value on the 1-bit tri-state status bit bus. The single status bit is output from the PU e.g 178, and then combined with the other PU e.g 178 status bits to update the Common Status Register 200. The microcode for determining the output status bit takes the following form:











# Bits
Description







2
Select unit whose status bit is to be output



00 = Adder unit



01 = Multiply/Logic unit



10 = Barrel Shift unit



11 = Reader unit


1
0 = Zero flag



1 = Negative flag


3
TOTAL









Within the ALU 188, the 2-bit Select Processor Block value is decoded into four 1-bit enable bits, with a different enable bit sent to each processor unit block. The status select bit (choosing Zero or Negative) is passed into all units to determine which bit is to be output onto the status bit bus.
Branching within Microcode
Each PU e.g 178 contains a 7 bit Program Counter (PC) that holds the current microcode address being executed. Normal program execution is linear, moving from address N in one cycle to address N+1 in the next cycle. Every cycle however, a microcode program has the ability to branch to a different location, or to test a status bit from the Common Status Register 200 and branch. The microcode for determining the next execution address takes the following form:











# Bits
Description
















2
00 = NOP (PC = PC+1)



01 = Branch always



10 = Branch if status bit clear



11 = Branch if status bit set


2
Select status bit from status word


7
Address to branch to (absolute address,



00-7F)


11
TOTAL









ALU 188

FIG. 5 illustrates the ALU 188 in more detail. Inside the ALU 188 are a number of specialized processing blocks, controlled by a microcode program. The specialized processing blocks include:

    
    
        Read Block 202, for accepting data from the input FIFOs
        Write Block 203, for sending data out via the output FIFOs
        Adder/Logical block 204, for addition & subtraction, comparisons and logical operations
        Multiply/Interpolate block 205, for multiple types of interpolations and multiply/accumulates
        Barrel Shift block 206, for shifting data as required
        In block 207, for accepting data from the external crossbar switch 183
        Out block 208, for sending data to the external crossbar switch 183
        Registers block 215, for holding data in temporary storage
    
    


Four specialized 32 bit registers hold the results of the 4 main processing blocks:

    
    
        M register 209 holds the result of the Multiply/Interpolate block
        L register 209 holds the result of the Adder/Logic block
        S register 209 holds the result of the Barrel Shifter block
        R register 209 holds the result of the Read Block 202
    
    


In addition there are two internal crossbar switches 213 and 214 for data transport. The various process blocks are further expanded in the following sections, together with the microcode definitions that pertain to each block. Note that the microcode is decoded within a block to provide the control signals to the various units within.
Data Transfers Between PUs e.g 178
Each PU e.g 178 is able to exchange data via the external crossbar. A PU e.g 178 takes two inputs and outputs two values to the external crossbar. In this way two operands for processing can be obtained in a single cycle, but cannot be actually used in an operation until the following cycle.
In 207
This block is illustrated in FIG. 6 and contains two registers, In1 and In2 that accept data from the external crossbar. The registers can be loaded each cycle, or can remain unchanged. The selection bits for choosing from among the 8 inputs are output to the external crossbar switch 183. The microcode takes the following form:











# Bits
Description







1
0 = NOP



1 = Load In1 from crossbar


3
Select Input 1 from external crossbar


1
0 = NOP



1 = Load In2 from crossbar


3
Select Input 2 from external crossbar


8
TOTAL









Out 208

Complementing In is Out 208. The Out block is illustrated in more detail in FIG. 7. Out contains two registers, Out1 and Out2, both of which are output to the external crossbar each cycle for use by other PUs e.g 178. The Write unit is also able to write one of Out1 or Out2 to one of the output FIFOs attached to the ALU 188. Finally, both registers are available as inputs to Crossbar1 213, which therefore makes the register values available as inputs to other units within the ALU 188. Each cycle either of the two registers can be updated according to microcode selection. The data loaded into the specified register can be one of D0-D3 (selected from Crossbar1 213) one of M, L, S, and R (selected from Crossbar2 214), one of 2 programmable constants, or the fixed values 0 or 1. The microcode for Out takes the following form:











# Bits
Description







1
0 = NOP



1 = Load Register


1
Select Register to load [Out1 or Out2]


4
Select input



[In1, In2, Out1, Out2, D0, D1, D2, D3, M, L, S, R, K1, K2, 0, 1]


6
TOTAL









Local Registers and Data Transfers within ALU 188
As noted previously, the ALU 188 contains four specialized 32-bit registers to hold the results of the 4 main processing blocks:

    
    
        M register 209 holds the result of the Multiply/Interpolate block
        L register 209 holds the result of the Adder/Logic block
        S register 209 holds the result of the Barrel Shifter block
        R register 209 holds the result of the Read Block 202
    
    


The CPU has direct access to these registers, and other units can select them as inputs via Crossbar2 214. Sometimes it is necessary to delay an operation for one or more cycles. The Registers block contains four 32-bit registers D0-D3 to hold temporary variables during processing. Each cycle one of the registers can be updated, while all the registers are output for other units to use via Crossbar1 213 (which also includes In1, In2, Out1 and Out2). The CPU has direct access to these registers. The data loaded into the specified register can be one of D0-D3 (selected from Crossbar1 213) one of M, L, S, and R (selected from Crossbar2 214), one of 2 programmable constants, or the fixed values 0 or 1. The Registers block 215 is illustrated in more detail in FIG. 8. The microcode for Registers takes the following form:











# Bits
Description







1
0 = NOP



1 = Load Register


2
Select Register to load [D0-D3]


4
Select input



[In1, In2, Out1, Out2, D0, D1, D2, D3, M, L, S, R, K1, K2, 0, 1]


7
TOTAL









Crossbar1 213

Crossbar1 213 is illustrated in more detail in FIG. 9. Crossbar1 213 is used to select from inputs In1, In2, Out1, Out2, D0-D3. 7 outputs are generated from Crossbar1 213: 3 to the Multiply/Interpolate Unit, 2 to the Adder Unit, 1 to the Registers unit and 1 to the Out unit. The control signals for Crossbar1 213 come from the various units that use the Crossbar inputs. There is no specific microcode that is separate for Crossbar1 213.
Crossbar2 214
Crossbar2 214 is illustrated in more detail in FIG. 10. Crossbar2 214 is used to select from the general ALU 188 registers M, L, S and R. 6 outputs are generated from Crossbar1 213: 2 to the Multiply/Interpolate Unit, 2 to the Adder Unit, 1 to the Registers unit and 1 to the Out unit. The control signals for Crossbar2 214 come from the various units that use the Crossbar inputs. There is no specific microcode that is separate for Crossbar2 214.
Data Transfers Between PUs e.g 178 and DRAM or External Processes
Returning to FIG. 4, PUs e.g 178 share data with each other directly via the external crossbar. They also transfer data to and from external processes as well as DRAM. Each PU e.g 178 has 2 I/O Address Generators 189, 190 for transferring data to and from DRAM. A PU e.g 178 can send data to DRAM via an I/O Address Generator's Output FIFO e.g. 186, or accept data from DRAM via an I/O Address Generator's Input FIFO 187. These FIFOs are local to the PU e.g 178. There is also a mechanism for transferring data to and from external processes in the form of a common VLIW Input FIFO 78 and a common VLIW Output FIFO 79, shared between all ALUs. The VLIW Input and Output FIFOs are only 8 bits wide, and are used for printing, Artcard reading, transferring data to the CPU etc. The local Input and Output FIFOs are 16 bits wide.
Read
The Read process block 202 of FIG. 5 is responsible for updating the ALU 188's R register 209, which represents the external input data to a VLIW microcoded process. Each cycle the Read Unit is able to read from either the common VLIW Input FIFO 78 (8 bits) or one of two local Input FIFOs (16 bits). A 32-bit value is generated, and then all or part of that data is transferred to the R register 209. The process can be seen in FIG. 11. The microcode for Read is described in the following table. Note that the interpretations of some bit patterns are deliberately chosen to aid decoding.











# Bits
Description
















2
00 = NOP



01 = Read from VLIW Input FIFO 78



10 = Read from Local FIFO 1



11 = Read from Local FIFO 2


1
How many significant bits



0 = 8 bits (pad with 0 or sign extend)



1 = 16 bits (only valid for Local FIFO reads)


1
0 = Treat data as unsigned (pad with 0)



1 = Treat data as signed (sign extend when reading



from FIFO)r


2
How much to shift data left by:



00 = 0 bits (no change)



01 = 8 bits



10 = 16 bits



11 = 24 bits


4
Which bytes of R to update (hi to lo order byte)



Each of the 4 bits represents 1 byte WriteEnable on R


10
TOTAL









Write

The Write process block is able to write to either the common VLIW Output FIFO 79 or one of the two local Output FIFOs each cycle. Note that since only 1 FIFO is written to in a given cycle, only one 16-bit value is output to all FIFOs, with the low 8 bits going to the VLIW Output FIFO 79. The microcode controls which of the FIFOs gates in the value. The process of data selection can be seen in more detail in FIG. 12. The source values Out1 and Out2 come from the Out block. They are simply two registers. The microcode for Write takes the following form:











# Bits
Description







2
00 = NOP



01 = Write VLIW Output FIFO 79



10 = Write local Output FIFO 1



11 = Write local Output FIFO 2


1
Select Output Value [Out1 or Out2]


3
Select part of Output Value to write (32 bits = 4 bytes ABCD)



000 = 0D



001 = 0D



010 = 0B



011 = 0A



100 = CD



101 = BC



110 = AB



111 = 0


6
TOTAL









Computational Blocks
Each ALU 188 has two computational process blocks, namely an Adder/Logic process block 204, and a Multiply/Interpolate process block 205. In addition there is a Barrel Shifter block to provide help to these computational blocks. Registers from the Registers block 215 can be used for temporary storage during pipelined operations.
Barrel Shifter
The Barrel Shifter process block 206 is shown in more detail in FIG. 13 and takes its input from the output of Adder/Logic or Multiply/Interpolate process blocks or the previous cycle's results from those blocks (ALU registers L and M). The 32 bits selected are barrel shifted an arbitrary number of bits in either direction (with sign extension as necessary), and output to the ALU 188's S register 209. The microcode for the Barrel Shift process block is described in the following table. Note that the interpretations of some bit patterns are deliberately chosen to aid decoding.











# Bits
Description
















3
000 = NOP



001 = Shift Left (unsigned)



010 = Reserved



011 = Shift Left (signed)



100 = Shift right (unsigned, no rounding)



101 = Shift right (unsigned, with rounding)



110 = Shift right (signed, no rounding)



111 = Shift right (signed, with rounding)


2
Select Input to barrel shift:



00 = Multiply/Interpolate result



01 = M



10 = Adder/Logic result



11 = L


5
# bits to shift


1
Ceiling of 255


1
Floor of 0 (signed data)


12
TOTAL









Adder/Logic 204

The Adder/Logic process block is shown in more detail in FIG. 14 and is designed for simple 32-bit addition/subtraction, comparisons, and logical operations. In a single cycle a single addition, comparison, or logical operation can be performed, with the result stored in the ALU 188's L register 209. There are two primary operands, A and B, which are selected from either of the two crossbars or from the 4 constant registers. One crossbar selection allows the results of the previous cycle's arithmetic operation to be used while the second provides access to operands previously calculated by this or another ALU 188. The CPU is the only unit that has write access to the four constants (K1-K4). In cases where an operation such as (A+B)×4 is desired, the direct output from the adder can be used as input to the Barrel Shifter, and can thus be shifted left 2 places without needing to be latched into the L register 209 first. The output from the adder can also be made available to the multiply unit for a multiply-accumulate operation. The microcode for the Adder/Logic process block is described in the following table. The interpretations of some bit patterns are deliberately chosen to aid decoding. Microcode bit interpretation for Adder/Logic unit











# Bits
Description
















4
0000 = A+B (carry in = 0)



0001 = A+B (carry in = carry out of previous operation)



0010 = A+B+1 (carry in = 1)



0011 = A+1 (increments A)



0100 = A−B−1 (carry in = 0)



0101 = A−B (carry in = carry out of previous operation)



0110 = A−B (carry in = 1)



0111 = A−1 (decrements A)



1000 = NOP



1001 = ABS(A−B)



1010 = MIN(A, B)



1011 = MAX(A, B)



1100 = A AND B (both A & B can be inverted, see below)



1101 = A OR B (both A & B can be inverted, see below)



1110 = A XOR B (both A & B can be inverted, see below)



1111 = A (A can be inverted, see below)


1
If logical operation:



0 = A=A



1 = A=NOT(A)



If Adder operation:



0 = A is unsigned



1 = A is signed


1
If logical operation:



0 = B=B



1 = B=NOT(B)



If Adder operation



0 = B is unsigned



1 = B is signed


4
Select A



[In1,In2,Out1,Out2,D0,D1,D2,D3,M,L,S,R,K1,K2,K3,K4]


4
Select B



[In1,In2,Out1,Out2,D0,D1,D2,D3,M,L,S,R,K1,K2,K3,K4]


14
TOTAL









Multiply/Interpolate 205

The Multiply/Interpolate process block is shown in more detail in FIG. 15 and is a set of four 8×8 interpolator units that are capable of performing four individual 8×8 interpolates per cycle, or can be combined to perform a single 16×16 multiply. This gives the possibility to perform up to 4 linear interpolations, a single bi-linear interpolation, or half of a tri-linear interpolation in a single cycle. The result of the interpolations or multiplication is stored in the ALU 188's M register 209. There are two primary operands, A and B, which are selected from any of the general registers in the ALU 188 or from four programmable constants internal to the Multiply/Interpolate process block. Each interpolator block functions as a simple 8 bit interpolator [result=A+(B−A)f] or as a simple 8×8 multiply [result=A*B]. When the operation is interpolation, A and B are treated as four 8 bit numbers A0 thru A3 (A0 is the low order byte), and B0 thru B3. Agen, Bgen, and Fgen are responsible for ordering the inputs to the Interpolate units so that they match the operation being performed. For example, to perform bilinear interpolation, each of the 4 values must be multiplied by a different factor & the result summed, while a 16×16 bit multiplication requires the factors to be 0. The microcode for the Adder/Logic process block is described in the following table. Note that the interpretations of some bit patterns are deliberately chosen to aid decoding.











# Bits
Description







4
0000 = (A10 * B10) + V



0001 = (A0 * B0) + (A1 * B1) + V



0010 = (A10 * B10) − V



0011 = V − (A10 * B10)



0100 = Interpolate A0,B0 by f0



0101 = Interpolate A0,B0 by f0, A1,B1 by f1



0110 = Interpolate A0,B0 by f0, A1,B1 by f1, A2,B2 by f2



0111 = Interpolate A0,B0 by f0, A1,B1 by f1, A2,B2 by f2, A3,B3



by f3



1000 = Interpolate 16 bits stage 1 [M = A10 * f10]



1001 = Interpolate 16 bits stage 2 [M = M + (A10 * f10)]



1010 = Tri-linear interpolate A by f stage 1



[M=A0f0+A1f1+A2f2+A3f3]



1011 = Tri-linear interpolate A by f stage 2



[M=M+A0f0+A1f1+A2f2+A3f3]



1100 = Bi-linear interpolate A by f stage 1 [M=A0f0+A1f1]



1101 = Bi-linear interpolate A by f stage 2 [M=M+A0f0+A1f1]



1110 = Bi-linear interpolate A by f complete



[M=A0f0+A1f1+A2f2+A3f3]



1111 = NOP


4
Select A [In1,In2,Out1,Out2,D0,D1,D2,D3,M,L,S,R,K1,K2,K3,K4]


4
Select B [In1,In2,Out1,Out2,D0,D1,D2,D3,M,L,S,R,K1,K2,K3,K4]


If


Mult:


4
Select V [In1,In2,Out1,Out2,D0,D1,D2,D3,K1,K2,K3,K4,Adder



result,M,0,1]


1
Treat A as signed


1
Treat B as signed


1
Treat V as signed


If


Interp:


4
Select basis for f



[In1,In2,Out1,Out2,D0,D1,D2,D3,K1,K2,K3,K4,X,X,X,X]


1
Select interpolation f generation from P1 or P2



Pn is interpreted as # fractional bits in f



If Pn=0, f is range 0 . . . 255 representing 0 . . . 1


2
Reserved


19 
TOTAL









The same 4 bits are used for the selection of V and f, although the last 4 options for V don't generally make sense as f values. Interpolating with a factor of 1 or 0 is pointless, and the previous multiplication or current result is unlikely to be a meaningful value for f.
I/O Address Generators 189, 190
The I/O Address Generators are shown in more detail in FIG. 16. A VLIW process does not access DRAM directly. Access is via 2 I/O Address Generators 189, 190, each with its own Input and Output FIFO. A PU e.g 178 reads data from one of two local Input FIFOs, and writes data to one of two local Output FIFOs. Each I/O Address Generator is responsible for reading data from DRAM and placing it into its Input FIFO, where it can be read by the PU e.g 178, and is responsible for taking the data from its Output FIFO (placed there by the PU e.g 178) and writing it to DRAM. The I/O Address Generator is a state machine responsible for generating addresses and control for data retrieval and storage in DRAM via the Data cache 76. It is customizable under CPU software control, but cannot be microcoded. The address generator produces addresses in two broad categories:

    
    
        Image Iterators, used to iterate (reading, writing or both) through pixels of an image in a variety of ways
        Table I/O, used to randomly access pixels in images, data in tables, and to simulate FIFOs in DRAM
    
    


Each of the I/O Address Generators 189, 190 has its own bus connection to the Data cache 76, making 2 bus connections per PU e.g 178, and a total of 8 buses over the entire VLIW Vector Processor 74. The Data cache 76 is able to service 4 of the maximum 8 requests from the 4 PUs e.g 178 each cycle. The Input and Output FIFOs are 8 entry deep 16-bit wide FIFOs. The various types of address generation (Image Iterators and Table I/O) are described in the subsequent sections.
Registers
The I/O Address Generator has a set of registers for that are used to control address generation. The addressing mode also determines how the data is formatted and sent into the local Input FIFO, and how data is interpreted from the local Output FIFO. The CPU is able to access the registers of the I/O Address Generator via the low speed bus. The first set of registers define the housekeeping parameters for the I/O Generator:












Register Name
# bits
Description







Reset
0
A write to this register halts any operations, and writes 0s to




all the data registers of the I/O Generator. The input and




output FIFOs are not cleared.


Go
0
A write to this register restarts the counters according to the




current setup. For example, if the I/O Generator is a Read




Iterator, and the Iterator is currently halfway through the




image, a write to Go will cause the reading to begin at the




start of the image again. While the I/O Generator is




performing, the Active bit of the Status register will be set.


Halt
0
A write to this register stops any current activity and clears




the Active bit of the Status register. If the Active bit is




already cleared, writing to this register has no effect.


Continue
0
A write to this register continues the I/O Generator from the




current setup. Counters are not reset, and FIFOs are not




cleared. A write to this register while the I/O Generator is active




has no effect.


ClearFIFOsOnGo
1
0 = Don't clear FIFOs on a write to the Go bit.




1 = Do clear FIFOs on a write to the Go bit.


Status
8
Status flags



















The Status register has the following values











Register Name
# bits
Description







Active
1
0 = Currently inactive





1 = Currently active



Reserved
7
—










Caching

Several registers are used to control the caching mechanism, specifying which cache group to use for inputs, outputs etc. See the section on the Data cache 76 for more information about cache groups.












Register Name
# bits
Description







CacheGroup1
4
Defines cache group to read data from


CacheGroup2
4
Defines which cache group to write data to,




and in the case of the ImagePyramidLookup




I/O mode, defines the cache to use for reading




the Level Information Table.









Image Iterators=Sequential Automatic Access to Pixels
The primary image pixel access method for software and hardware algorithms is via Image Iterators. Image iterators perform all of the addressing and access to the caches of the pixels within an image channel and read, write or read & write pixels for their client. Read Iterators read pixels in a specific order for their clients, and Write Iterators write pixels in a specific order for their clients. Clients of Iterators read pixels from the local Input FIFO or write pixels via the local Output FIFO.
Read Image Iterators read through an image in a specific order, placing the pixel data into the local Input FIFO. Every time a client reads a pixel from the Input FIFO, the Read Iterator places the next pixel from the image (via the Data cache 76) into the FIFO.
Write Image Iterators write pixels in a specific order to write out the entire image. Clients write pixels to the Output FIFO that is in turn read by the Write Image Iterator and written to DRAM via the Data cache 76.
Typically a VLIW process will have its input tied to a Read Iterator, and output tied to a corresponding Write Iterator. From the PU e.g 178 microcode program's perspective, the FIFO is the effective interface to DRAM. The actual method of carrying out the storage (apart from the logical ordering of the data) is not of concern. Although the FIFO is perceived to be effectively unlimited in length, in practice the FIFO is of limited length, and there can be delays storing and retrieving data, especially if several memory accesses are competing. A variety of Image Iterators exist to cope with the most common addressing requirements of image processing algorithms. In most cases there is a corresponding Write Iterator for each Read Iterator. The different Iterators are listed in the following table:














Read Iterators
Write Iterators









Sequential Read
Sequential Write



Box Read
—



Vertical Strip Read
Vertical Strip Write




















The 4 bit Address Mode Register is used to determine the


Iterator type:








Bit #
Address Mode





3
0 = This addressing mode is an Iterator


2 to 0
Iterator Mode



001 = Sequential Iterator



010 = Box [read only]



100 = Vertical Strip



remaining bit patterns are reserved



















The Access Specific registers are used as follows:









Register Name
LocalName
Description





AccessSpecific1
Flags
Flags used for reading and writing


AccessSpecific2
XBoxSize
Determines the size in X of Box Read.




Valid values are 3, 5, and 7.


AccessSpecific3
YBoxSize
Determines the size in Y of Box Read.




Valid values are 3, 5, and 7.


AccessSpecific4
BoxOffset
Offset between one pixel center and




the next during a Box Read only.




Usual value is 1, but other useful




values include 2, 4, 8 . . . See Box Read




for more details.









The Flags register (AccessSpecific1) contains a number of flags used to determine factors affecting the reading and writing of data. The Flags register has the following composition:












Label
#bits
Description

















ReadEnable
1
Read data from DRAM


WriteEnable
1
Write data to DRAM [not valid for Box mode]


PassX
1
Pass X (pixel) ordinate back to Input FIFO


PassY
1
Pass Y (row) ordinate back to Input FIFO


Loop
1
0 = Do not loop through data




1 = Loop through data


Reserved
11
Must be 0





Notes on ReadEnable and WriteEnable:


When ReadEnable is set, the I/O Address Generator acts as a Read Iterator, and therefore reads the image in a particular order, placing the pixels into the Input FIFO.


When WriteEnable is set, the I/O Address Generator acts as a Write Iterator, and therefore writes the image in a particular order, taking the pixels from the Output FIFO.


When both ReadEnable and WriteEnable are set, the I/O Address Generator acts as a Read Iterator and as a Write Iterator, reading pixels into the Input FIFO, and writing pixels from the Output FIFO. Pixels are only written after they have been read - i.e. the Write Iterator will never go faster than the Read Iterator.


Whenever this mode is used, care should be taken to ensure balance between in and out processing by the VLIW microcode. Note that separate cache groups can be specified on reads and writes by loading different values in CacheGroup 1 and CacheGroup2.


Notes on PassX and PassY:


If PassX and PassY are both set, the Y ordinate is placed into the Input FIFO before the X ordinate.


PassX and PassY are only intended to be set when the ReadEnable bit is clear. Instead of passing the ordinates to the address generator, the ordinates are placed directly into the Input FIFO. The ordinates advance as they are removed from the FIFO.


If WriteEnable bit is set, the VLIW program must ensure that it balances reads of ordinates from the Input FIFO with writes to the Output FIFO, as writes will only occur up to the ordinates (see note on ReadEnable and WriteEnable above).


Notes on Loop:


If the Loop bit is set, reads will recommence at [StartPixel, StartRow] once it has reached [EndPixel, EndRow]. This is ideal for processing a structure such a convolution kernel or a dither cell matrix, where the data must be read repeatedly.


Looping with ReadEnable and WriteEnable set can be useful in an environment keeping a single line history, but only where it is useful to have reading occur before writing. For a FIFO effect (where writing occurs before reading in a length constrained fashion), use an appropriate Table I/O addressing mode instead of an Image Iterator.


Looping with only WriteEnable set creates a written window of the last N pixels. This can be used with an asynchronous process that reads the data from the window. The Artcard Reading algorithm makes use of this mode.






Sequential Read and Write Iterators

FIG. 17 illustrates the pixel data format. The simplest Image Iterators are the Sequential Read Iterator and corresponding Sequential Write Iterator. The Sequential Read Iterator presents the pixels from a channel one line at a time from top to bottom, and within a line, pixels are presented left to right. The padding bytes are not presented to the client. It is most useful for algorithms that must perform some process on each pixel from an image but don't care about the order of the pixels being processed, or want the data specifically in this order. Complementing the Sequential Read Iterator is the Sequential Write Iterator. Clients write pixels to the Output FIFO. A Sequential Write Iterator subsequently writes out a valid image using appropriate caching and appropriate padding bytes. Each Sequential Iterator requires access to 2 cache lines. When reading, while 32 pixels are presented from one cache line, the other cache line can be loaded from memory. When writing, while 32 pixels are being filled up in one cache line, the other can be being written to memory.
A process that performs an operation on each pixel of an image independently would typically use a Sequential Read Iterator to obtain pixels, and a Sequential Write Iterator to write the new pixel values to their corresponding locations within the destination image. Such a process is shown in FIG. 18.
In most cases, the source and destination images are different, and are represented by 2 I/O Address Generators 189, 190. However it can be valid to have the source image and destination image to be the same, since a given input pixel is not read more than once. In that case, then the same Iterator can be used for both input and output, with both the ReadEnable and WriteEnable registers set appropriately. For maximum efficiency, 2 different cache groups should be used—one for reading and the other for writing. If data is being created by a VLIW process to be written via a Sequential Write Iterator, the PassX and PassY flags can be used to generate coordinates that are then passed down the Input FIFO. The VLIW process can use these coordinates and create the output data appropriately.
Box Read Iterator
The Box Read Iterator is used to present pixels in an order most useful for performing operations such as general-purpose filters and convolve. The Iterator presents pixel values in a square box around the sequentially read pixels. The box is limited to being 1, 3, 5, or 7 pixels wide in X and Y (set XBoxSize and YBoxSize—they must be the same value or 1 in one dimension and 3, 5, or 7 in the other). The process is shown in FIG. 19:
BoxOffset: This special purpose register is used to determine a sub-sampling in terms of which input pixels will be used as the center of the box. The usual value is 1, which means that each pixel is used as the center of the box. The value “2” would be useful in scaling an image down by 4:1 as in the case of building an image pyramid. Using pixel addresses from the previous diagram, the box would be centered on pixel 0, then 2, 8, and 10. The Box Read Iterator requires access to a maximum of 14 (2×7) cache lines. While pixels are presented from one set of 7 lines, the other cache lines can be loaded from memory.
Box Write Iterator
There is no corresponding Box Write Iterator, since the duplication of pixels is only required on input. A process that uses the Box Read Iterator for input would most likely use the Sequential Write Iterator for output since they are in sync. A good example is the convolver, where N input pixels are read to calculate 1 output pixel. The process flow is as illustrated in FIG. 20. The source and destination images should not occupy the same memory when using a Box Read Iterator, as subsequent lines of an image require the original (not newly calculated) values.
Vertical-Strip Read and Write Iterators
In some instances it is necessary to write an image in output pixel order, but there is no knowledge about the direction of coherence in input pixels in relation to output pixels. An example of this is rotation. If an image is rotated 90 degrees, and we process the output pixels horizontally, there is a complete loss of cache coherence. On the other hand, if we process the output image one cache line's width of pixels at a time and then advance to the next line (rather than advance to the next cache-line's worth of pixels on the same line), we will gain cache coherence for our input image pixels. It can also be the case that there is known ‘block’ coherence in the input pixels (such as color coherence), in which case the read governs the processing order, and the write, to be synchronized, must follow the same pixel order. The order of pixels presented as input (Vertical-Strip Read), or expected for output (Vertical-Strip Write) is the same. The order is pixels 0 to 31 from line 0, then pixels 0 to 31 of line 1 etc for all lines of the image, then pixels 32 to 63 of line 0, pixels 32 to 63 of line 1 etc. In the final vertical strip there may not be exactly 32 pixels wide. In this case only the actual pixels in the image are presented or expected as input. This process is illustrated in FIG. 21.
process that requires only a Vertical-Strip Write Iterator will typically have a way of mapping input pixel coordinates given an output pixel coordinate. It would access the input image pixels according to this mapping, and coherence is determined by having sufficient cache lines on the ‘random-access’ reader for the input image. The coordinates will typically be generated by setting the PassX and PassY flags on the VerticalStripWrite Iterator, as shown in the process overview illustrated in FIG. 22.
It is not meaningful to pair a Write Iterator with a Sequential Read Iterator or a Box read Iterator, but a Vertical-Strip Write Iterator does give significant improvements in performance when there is a non trivial mapping between input and output coordinates.
It can be meaningful to pair a Vertical Strip Read Iterator and Vertical Strip Write Iterator. In this case it is possible to assign both to a single ALU 188 if input and output images are the same. If coordinates are required, a further Iterator must be used with PassX and PassY flags set. The Vertical Strip Read/Write Iterator presents pixels to the Input FIFO, and accepts output pixels from the Output FIFO. Appropriate padding bytes will be inserted on the write. Input and output require a minimum of 2 cache lines each for good performance.
Table I/O Addressing Modes
It is often necessary to lookup values in a table (such as an image). Table I/O addressing modes provide this functionality, requiring the client to place the index/es into the Output FIFO. The I/O Address Generator then processes the index/es, looks up the data appropriately, and returns the looked-up values in the Input FIFO for subsequent processing by the VLIW client.
1D, 2D and 3D tables are supported, with particular modes targeted at interpolation. To reduce complexity on the VLIW client side, the index values are treated as fixed-point numbers, with AccessSpecific registers defining the fixed point and therefore which bits should be treated as the integer portion of the index. Data formats are restricted forms of the general Image Characteristics in that the PixelOffset register is ignored, the data is assumed to be contiguous within a row, and can only be 8 or 16 bits (1 or 2 bytes) per data element. The 4 bit Address Mode Register is used to determine the I/O type:











Bit #
Address Mode







3
1 = This addressing mode is Table I/O


2 to 0
000 = 1D Direct Lookup



001 = 1D Interpolate (linear)



010 = DRAM FIFO



011 = Reserved



100 = 2D Interpolate (bi-linear)



101 = Reserved



110 = 3D Interpolate (tri-linear)



111 = Image Pyramid Lookup









The access specific registers are:













Register Name
LocalName
#bits
Description







AccessSpecific1
Flags
8
General flags for reading and





writing. See below for more





information.


AccessSpecific2
FractX
8
Number of fractional bits in X





index


AccessSpecific3
FractY
8
Number of fractional bits in Y





index


AccessSpecific4
FractZ
8
Number of fractional bits in Z





index


(low 8 bits/next
ZOffset
12 or
See below


12 or 24 bits))

24









FractX, FractY, and FractZ are used to generate addresses based on indexes, and interpret the format of the index in terms of significant bits and integer/fractional components. The various parameters are only defined as required by the number of dimensions in the table being indexed. A 1D table only needs FractX, a 2D table requires FractX and FractY. Each Fract_ value consists of the number of fractional bits in the corresponding index. For example, an X index may be in the format 5:3. This would indicate 5 bits of integer, and 3 bits of fraction. FractX would therefore be set to 3. A simple 1D lookup could have the format 8:0, i.e. no fractional component at all. FractX would therefore be 0. ZOffset is only required for 3D lookup and takes on two different interpretations. It is described more fully in the 3D-table lookup section. The Flags register (AccessSpecific1) contains a number of flags used to determine factors affecting the reading (and in one case, writing) of data. The Flags register has the following composition:















Label
#bits
Description









ReadEnable
1
Read data from DRAM



WriteEnable
1
Write data to DRAM [only valid for





1D direct lookup]



DataSize
1
0 = 8 bit data





1 = 16 bit data



Reserved
5
Must be 0










With the exception of the 1D Direct Lookup and DRAM FIFO, all Table I/O modes only support reading, and not writing. Therefore the ReadEnable bit will be set and the WriteEnable bit will be clear for all I/O modes other than these two modes. The 1D Direct Lookup supports 3 modes:

    
    
        Read only, where the ReadEnable bit is set and the WriteEnable bit is clear
        Write only, where the ReadEnable bit is clear and the WriteEnable bit is clear
        Read-Modify-Write, where both ReadEnable and the WriteEnable bits are set
    
    


The different modes are described in the 1D Direct Lookup section below. The DRAM FIFO mode supports only 1 mode:
Write-Read mode, where both ReadEnable and the WriteEnable bits are set This mode is described in the DRAM FIFO section below. The DataSize flag determines whether the size of each data elements of the table is 8 or 16 bits. Only the two data sizes are supported. 32 bit elements can be created in either of 2 ways depending on the requirements of the process:

    
    
        Reading from 216-bit tables simultaneously and combining the result. This is convenient if timing is an issue, but has the disadvantage of consuming 2 I/O Address Generators 189, 190, and each 32-bit element is not readable by the CPU as a 32-bit entity.
        Reading from a 16-bit table twice and combining the result. This is convenient since only 1 lookup is used, although different indexes must be generated and passed into the lookup.

1 Dimensional Structures

Direct Lookup

    
    


A direct lookup is a simple indexing into a 1 dimensional lookup table. Clients can choose between 3 access modes by setting appropriate bits in the Flags register:

    
    
        Read only
        Write only
        Read-Modify-Write

Read Only

    
    


A client passes the fixed-point index X into the Output FIFO, and the 8 or 16-bit value at Table[Int(X)] is returned in the Input FIFO. The fractional component of the index is completely ignored. If the index is out of bounds, the DuplicateEdge flag determines whether the edge pixel or ConstantPixel is returned. The address generation is straightforward:

    
    
        If DataSize indicates 8 bits, X is barrel-shifted right FractX bits, and the result is added to the table's base address ImageStart.
        If DataSize indicates 16 bits, X is barrel-shifted right FractX bits, and the result shifted left 1 bit (bit0 becomes 0) is added to the table's base address Image Start.
    
    


The 8 or 16-bit data value at the resultant address is placed into the Input FIFO. Address generation takes 1 cycle, and transferring the requested data from the cache to the Output FIFO also takes 1 cycle (assuming a cache hit). For example, assume we are looking up values in a 256-entry table, where each entry is 16 bits, and the index is a 12 bit fixed-point format of 8:4. FractX should be 4, and DataSize 1. When an index is passed to the lookup, we shift right 4 bits, then add the result shifted left 1 bit to ImageStart.
Write Only
A client passes the fixed-point index X into the Output FIFO followed by the 8 or 16-bit value that is to be written to the specified location in the table. A complete transfer takes a minimum of 2 cycles. 1 cycle for address generation, and 1 cycle to transfer the data from the FIFO to DRAM. There can be an arbitrary number of cycles between a VLIW process placing the index into the FIFO and placing the value to be written into the FIFO. Address generation occurs in the same way as Read Only mode, but instead of the data being read from the address, the data from the Output FIFO is written to the address. If the address is outside the table range, the data is removed from the FIFO but not written to DRAM.
Read-Modify-Write
A client passes the fixed-point index X into the Output FIFO, and the 8 or 16-bit value at Table[Int(X)] is returned in the Input FIFO. The next value placed into the Output FIFO is then written to Table[Int(X)], replacing the value that had been returned earlier. The general processing loop then, is that a process reads from a location, modifies the value, and writes it back. The overall time is 4 cycles:

    
    
        Generate address from index
        Return value from table
        Modify value in some way
        Write it back to the table
    
    


There is no specific read/write mode where a client passes in a flag saying “read from X” or “write to X”. Clients can simulate a “read from X” by writing the original value, and a “write to X” by simply ignoring the returned value. However such use of the mode is not encouraged since each action consumes a minimum of 3 cycles (the modify is not required) and 2 data accesses instead of 1 access as provided by the specific Read and Write modes.
Interpolate Table
This is the same as a Direct Lookup in Read mode except that two values are returned for a given fixed-point index X instead of one. The values returned are Table[Int(X)], and Table[Int(X)+1]. If either index is out of bounds the DuplicateEdge flag determines whether the edge pixel or ConstantPixel is returned. Address generation is the same as Direct Lookup, with the exception that the second address is simply Address1+1 or 2 depending on 8 or 16 bit data. Transferring the requested data to the Output FIFO takes 2 cycles (assuming a cache hit), although two 8-bit values may actually be returned from the cache to the Address Generator in a single 16-bit fetch.
DRAM FIFO
A special case of a read/write 1D table is a DRAM FIFO. It is often necessary to have a simulated FIFO of a given length using DRAM and associated caches. With a DRAM FIFO, clients do not index explicitly into the table, but write to the Output FIFO as if it was one end of a FIFO and read from the Input FIFO as if it was the other end of the same logical FIFO. 2 counters keep track of input and output positions in the simulated FIFO, and cache to DRAM as needed. Clients need to set both ReadEnable and WriteEnable bits in the Flags register. An example use of a DRAM FIFO is keeping a single line history of some value. The initial history is written before processing begins. As the general process goes through a line, the previous line's value is retrieved from the FIFO, and this line's value is placed into the FIFO (this line will be the previous line when we process the next line). So long as input and outputs match each other on average, the Output FIFO should always be full. Consequently there is effectively no access delay for this kind of FIFO (unless the total FIFO length is very small—say 3 or 4 bytes, but that would defeat the purpose of the FIFO).
2 Dimensional Tables
Direct Lookup
A 2 dimensional direct lookup is not supported. Since all cases of 2D lookups are expected to be accessed for bi-linear interpolation, a special bi-linear lookup has been implemented.
Bi-Linear Lookup
This kind of lookup is necessary for bi-linear interpolation of data from a 2D table. Given fixed-point X and Y coordinates (placed into the Output FIFO in the order Y, X), 4 values are returned after lookup. The values (in order) are:

    
    
        Table[Int(X), Int(Y)]
        Table[Int(X)+1, Int(Y)]
        Table[Int(X), Int(Y)+1]
        Table[Int(X)+1, Int(Y)+1]
    
    


The order of values returned gives the best cache coherence. If the data is 8-bit, 2 values are returned each cycle over 2 cycles with the low order byte being the first data element. If the data is 16-bit, the 4 values are returned in 4 cycles, 1 entry per cycle. Address generation takes 2 cycles. The first cycle has the index (Y) barrel-shifted right FractY bits being multiplied by RowOffset, with the result added to ImageStart. The second cycle shifts the X index right by FractX bits, and then either the result (in the case of 8 bit data) or the result shifted left 1 bit (in the case of 16 bit data) is added to the result from the first cycle. This gives us address Adr=address of Table[Int(X), Int(Y)]:

Adr=ImageStart+ShiftRight(Y,FractY)*RowOffset)+ShiftRight(X,FractX)

We keep a copy of Adr in AdrOld for use fetching subsequent entries.

    
    
        If the data is 8 bits, the timing is 2 cycles of address generation, followed by 2 cycles of data being returned (2 table entries per cycle).
        If the data is 16 bits, the timing is 2 cycles of address generation, followed by 4 cycles of data being returned (1 entry per cycle)
    
    


The following 2 tables show the method of address calculation for 8 and 16 bit data sizes:











Cycle
Calculation while fetching 2 × 8-bit data entries from Adr







1
Adr = Adr + RowOffset


2
<preparing next lookup>




















Cycle
Calculation while fetching 1 × 16-bit data entry from Adr







1
Adr = Adr + 2


2
Adr = AdrOld + RowOffset


3
Adr = Adr + 2


4
<preparing next lookup>









In both cases, the first cycle of address generation can overlap the insertion of the X index into the FIFO, so the effective timing can be as low as 1 cycle for address generation, and 4 cycles of return data. If the generation of indexes is 2 steps ahead of the results, then there is no effective address generation time, and the data is simply produced at the appropriate rate (2 or 4 cycles per set).
3 Dimensional Lookup
Direct Lookup
Since all cases of 2D lookups are expected to be accessed for tri-linear interpolation, two special tri-linear lookups have been implemented. The first is a straightforward lookup table, while the second is for tri-linear interpolation from an Image Pyramid.
Tri-Linear Lookup
This type of lookup is useful for 3D tables of data, such as color conversion tables. The standard image parameters define a single XY plane of the data—i.e. each plane consists of ImageHeight rows, each row containing RowOffset bytes. In most circumstances, assuming contiguous planes, one XY plane will be ImageHeight×RowOffset bytes after another. Rather than assume or calculate this offset, the software via the CPU must provide it in the form of a 12-bit ZOffset register. In this form of lookup, given 3 fixed-point indexes in the order Z, Y, X, 8 values are returned in order from the lookup table:

    
    
        Table[Int(X), Int(Y), Int(Z)]
        Table[Int(X)+1, Int(Y), Int(Z)]
        Table[Int(X), Int(Y)+1, Int(Z)]
        Table[Int(X)+1, Int(Y)+1, Int(Z)]
        Table[Int(X), Int(Y), Int(Z)+1]
        Table[Int(X)+1, Int(Y), Int(Z)+1]
        Table[Int(X), Int(Y)+1, Int(Z)+1]
        Table[Int(X)+1, Int(Y)+1, Int(Z)+1]
    
    


The order of values returned gives the best cache coherence. If the data is 8-bit, 2 values are returned each cycle over 4 cycles with the low order byte being the first data element. If the data is 16-bit, the 4 values are returned in 8 cycles, 1 entry per cycle. Address generation takes 3 cycles. The first cycle has the index (Z) barrel-shifted right FractZ bits being multiplied by the 12-bit ZOffset and added to ImageStart. The second cycle has the index (Y) barrel-shifted right FractY bits being multiplied by RowOffset, with the result added to the result of the previous cycle. The second cycle shifts the X index right by FractX bits, and then either the result (in the case of 8 bit data) or the result shifted left 1 bit (in the case of 16 bit data) is added to the result from the second cycle. This gives us address Adr=address of Table[Int(X), Int(Y), Int(Z)]:

Adr=ImageStart+(ShiftRight(Z,FractZ)*ZOffset)+(ShiftRight(Y,FractY)*RowOffset)+ShiftRight(X,FractX)

We keep a copy of Adr in AdrOld for use fetching subsequent entries.

    
    
        If the data is 8 bits, the timing is 2 cycles of address generation, followed by 2 cycles of data being returned (2 table entries per cycle).
        If the data is 16 bits, the timing is 2 cycles of address generation, followed by 4 cycles of data being returned (1 entry per cycle)
    
    


The following 2 tables show the method of address calculation for 8 and 16 bit data sizes:











Cycle
Calculation while fetching 2 × 8-bit data entries from Adr







1
Adr = Adr + RowOffset


2
Adr = AdrOld + ZOffset


3
Adr = Adr + RowOffset


4
<preparing next lookup>




















Cycle
Calculation while fetching 1 × 16-bit data entries from Adr







1
Adr = Adr + 2


2
Adr = AdrOld + RowOffset


3
Adr = Adr + 2


4
Adr, AdrOld = AdrOld + Zoffset


5
Adr = Adr + 2


6
Adr = AdrOld + RowOffset


7
Adr = Adr + 2


8
<preparing next lookup>









In both cases, the cycles of address generation can overlap the insertion of the indexes into the FIFO, so the effective timing for a single one-off lookup can be as low as 1 cycle for address generation, and 4 cycles of return data. If the generation of indexes is 2 steps ahead of the results, then there is no effective address generation time, and the data is simply produced at the appropriate rate (4 or 8 cycles per set).
Image Pyramid Lookup
During brushing, tiling, and warping it is necessary to compute the average color of a particular area in an image. Rather than calculate the value for each area given, these functions make use of an image pyramid. The description and construction of an image pyramid is detailed in the section on Internal Image Formats in the DRAM interface 81 chapter of this document. This section is concerned with a method of addressing given pixels in the pyramid in terms of 3 fixed-point indexes ordered: level (Z), Y, and X. Note that Image Pyramid lookup assumes 8 bit data entries, so the DataSize flag is completely ignored. After specification of Z, Y, and X, the following 8 pixels are returned via the Input FIFO:

    
    
        The pixel at [Int(X), Int(Y)], level Int(Z)
        The pixel at [Int(X)+1, Int(Y)], level Int(Z)
        The pixel at [Int(X), Int(Y)+1], level Int(Z)
        The pixel at [Int(X)+1, Int(Y)+1], level Int(Z)
        The pixel at [Int(X), Int(Y)], level Int(Z)+1
        The pixel at [Int(X)+1, Int(Y)], level Int(Z)+1
        The pixel at [Int(X), Int(Y)+1], level Int(Z)+1
        The pixel at [Int(X)+1, Int(Y)+1], level Int(Z)+1
    
    


The 8 pixels are returned as 4×16 bit entries, with X and X+1 entries combined hi/lo. For example, if the scaled (X, Y) coordinate was (10.4, 12.7) the first 4 pixels returned would be: (10, 12), (11, 12), (10, 13) and (11, 13). When a coordinate is outside the valid range, clients have the choice of edge pixel duplication or returning of a constant color value via the DuplicateEdgePixels and ConstantPixel registers (only the low 8 bits are used). When the Image Pyramid has been constructed, there is a simple mapping from level 0 coordinates to level Z coordinates. The method is simply to shift the X or Y coordinate right by Z bits. This must be done in addition to the number of bits already shifted to retrieve the integer portion of the coordinate (i.e. shifting right FractX and FractY bits for X and Y ordinates respectively). To find the ImageStart and RowOffset value for a given level of the image pyramid, the 24-bit ZOffset register is used as a pointer to a Level Information Table. The table is an array of records, each representing a given level of the pyramid, ordered by level number. Each record consists of a 16-bit offset ZOffset from ImageStart to that level of the pyramid (64-byte aligned address as lower 6 bits of the offset are not present), and a 12 bit ZRowOffset for that level. Element 0 of the table would contain a ZOffset of 0, and a ZRowOffset equal to the general register RowOffset, as it simply points to the full sized image. The ZOffset value at element N of the table should be added to ImageStart to yield the effective ImageStart of level N of the image pyramid. The RowOffset value in element N of the table contains the RowOffset value for level N. The software running on the CPU must set up the table appropriately before using this addressing mode. The actual address generation is outlined here in a cycle by cycle description:














Load
From



Cycle
Register
Address
Other Operations







0
—
—
ZAdr = ShiftRight(Z, FractZ) + ZOffset





ZInt = ShiftRight(Z, FractZ)


1
ZOffset
Zadr
ZAdr += 2





YInt = ShiftRight(Y, FractY)


2
ZRowOffset
ZAdr
ZAdr += 2





YInt = ShiftRight(YInt, ZInt)





Adr = ZOffset + ImageStart


3
ZOffset
ZAdr
ZAdr += 2





Adr += ZrowOffset * YInt





XInt = ShiftRight(X, FractX)


4
ZAdr
ZAdr
Adr += ShiftRight(XInt, ZInt)





ZOffset += ShiftRight(XInt, 1)


5
FIFO
Adr
Adr += ZrowOffset





ZOffset += ImageStart


6
FIFO
Adr
Adr = (ZAdr * ShiftRight(Yint, 1)) +





ZOffset


7
FIFO
Adr
Adr += Zadr


8
FIFO
Adr
<Cycle 0 for next retrieval>









The address generation as described can be achieved using a single Barrel Shifter, 2 adders, and a single 16×16 multiply/add unit yielding 24 bits. Although some cycles have 2 shifts, they are either the same shift value (i.e. the output of the Barrel Shifter is used two times) or the shift is 1 bit, and can be hard wired. The following internal registers are required: ZAdr, Adr, ZInt, YInt, XInt, ZRowOffset, and ZImageStart. The _Int registers only need to be 8 bits maximum, while the others can be up to 24 bits. Since this access method only reads from, and does not write to image pyramids, the CacheGroup2 is used to lookup the Image Pyramid Address Table (via ZAdr). CacheGroup1 is used for lookups to the image pyramid itself (via Adr). The address table is around 22 entries (depending on original image size), each of 4 bytes. Therefore 3 or 4 cache lines should be allocated to CacheGroup2, while as many cache lines as possible should be allocated to CacheGroup1. The timing is 8 cycles for returning a set of data, assuming that Cycle 8 and Cycle 0 overlap in operation—i.e. the next request's Cycle 0 occurs during Cycle 8. This is acceptable since Cycle 0 has no memory access, and Cycle 8 has no specific operations.
Generation of Coordinates Using VLIW Vector Processor 74
Some functions that are linked to Write Iterators require the X and/or Y coordinates of the current pixel being processed in part of the processing pipeline. Particular processing may also need to take place at the end of each row, or column being processed. In most cases, the PassX and PassY flags should be sufficient to completely generate all coordinates. However, if there are special requirements, the following functions can be used. The calculation can be spread over a number of ALUs, for a single cycle generation, or be in a single ALU 188 for a multi-cycle generation.
Generate Sequential [X Y]
When a process is processing pixels in sequential order according to the Sequential Read Iterator (or generating pixels and writing them out to a Sequential Write Iterator), the following process can be used to generate X, Y coordinates instead of PassX/PassY flags as shown in FIG. 23.
The coordinate generator counts up to ImageWidth in the X ordinate, and once per ImageWidth pixels increments the Y ordinate. The actual process is illustrated in FIG. 24, where the following constants are set by software:











Constant
Value







K1
ImageWidth


K2
ImageHeight (optional)









The following registers are used to hold temporary variables:











Variable
Value







Reg1
X (starts at 0 each line)


Reg2
Y (starts at 0)









The requirements are summarized as follows:



















Requirements
*+
+
R
K
LU
Iterators









General
0
3/4
2
1/2
0
0



TOTAL
0
3/4
2
1/2
0
0










Generate Vertical Strip [X Y]
When a process is processing pixels in order to write them to a Vertical Strip Write Iterator, and for some reason cannot use the PassX/PassY flags, the process as illustrated in FIG. 25 can be used to generate X, Y coordinates. The coordinate generator simply counts up to ImageWidth in the X ordinate, and once per ImageWidth pixels increments the Y ordinate. The actual process is illustrated in FIG. 26, where the following constants are set by software:











Constant
Value







K1
32


K2
ImageWidth


K3
ImageHeight









The following registers are used to hold temporary variables:











Variable
Value







Reg1
StartX (starts at 0, and is incremented by 32 once per vertical



strip)


Reg2
X


Reg3
EndX (starts at 32 and is incremented by 32 to a maximum of



ImageWidth) once per vertical strip)


Reg4
Y









The requirements are summarized as follows:



















Requirements
*+
+
R
K
LU
Iterators









General
0
4
4
3
0
0



TOTAL
0
4
4
3
0
0










The calculations that occur once per vertical strip (2 additions, one of which has an associated MIN) are not included in the general timing statistics because they are not really part of the per pixel timing. However they do need to be taken into account for the programming of the microcode for the particular function.
Image Sensor Interface (ISI 83)
The Image Sensor Interface (ISI 83) takes data from the CMOS Image Sensor and makes it available for storage in DRAM. The image sensor has an aspect ratio of 3:2, with a typical resolution of 750×500 samples, yielding 375K (8 bits per pixel). Each 2×2 pixel block has the configuration as shown in FIG. 27. The ISI 83 is a state machine that sends control information to the Image Sensor, including frame sync pulses and pixel clock pulses in order to read the image. Pixels are read from the image sensor and placed into the VLIW Input FIFO 78. The VLIW is then able to process and/or store the pixels. This is illustrated further in FIG. 28. The ISI 83 is used in conjunction with a VLIW program that stores the sensed Photo Image in DRAM. Processing occurs in 2 steps:

    
    
        A small VLIW program reads the pixels from the FIFO and writes them to DRAM via a Sequential Write Iterator.
        The Photo Image in DRAM is rotated 90, 180 or 270 degrees according to the orientation of the camera when the photo was taken.
    
    


If the rotation is 0 degrees, then step 1 merely writes the Photo Image out to the final Photo Image location and step 2 is not performed. If the rotation is other than 0 degrees, the image is written out to a temporary area (for example into the Print Image memory area), and then rotated during step 2 into the final Photo Image location. Step 1 is very simple microcode, taking data from the VLIW Input FIFO 78 and writing it to a Sequential Write Iterator. Step 2's rotation is accomplished by using the accelerated Vark Affine Transform function. The processing is performed in 2 steps in order to reduce design complexity and to re-use the Vark affine transform rotate logic already required for images. This is acceptable since both steps are completed in approximately 0.03 seconds, a time imperceptible to the operator of the Artcam. Even so, the read process is sensor speed bound, taking 0.02 seconds to read the full frame, and approximately 0.01 seconds to rotate the image.
The orientation is important for converting between the sensed Photo Image and the internal format image, since the relative positioning of R, G, and B pixels changes with orientation. The processed image may also have to be rotated during the Print process in order to be in the correct orientation for printing. The 3D model of the Artcam has 2 image sensors, with their inputs multiplexed to a single ISI 83 (different microcode, but same ACP 31). Since each sensor is a frame store, both images can be taken simultaneously, and then transferred to memory one at a time.
Display Controller 88
When the “Take” button on an Artcam is half depressed, the TFT will display the current image from the image sensor (converted via a simple VLIW process). Once the Take button is fully depressed, the Taken Image is displayed. When the user presses the Print button and image processing begins, the TFT is turned off. Once the image has been printed the TFT is turned on again. The Display Controller 88 is used in those Artcam models that incorporate a flat panel display. An example display is a TFT LCD of resolution 240×160 pixels. The structure of the Display Controller 88 is illustrated in FIG. 29. The Display Controller 88 State Machine contains registers that control the timing of the Sync Generation, where the display image is to be taken from (in DRAM via the Data cache 76 via a specific Cache Group), and whether the TFT should be active or not (via TFT Enable) at the moment. The CPU can write to these registers via the low speed bus. Displaying a 240×160 pixel image on an RGB TFT requires 3 components per pixel. The image taken from DRAM is displayed via 3 DACs, one for each of the R, G, and B output signals. At an image refresh rate of 30 frames per second (60 fields per second) the Display Controller 88 requires data transfer rates of:

240×160×3×30=3.5 MB per second

This data rate is low compared to the rest of the system. However it is high enough to cause VLIW programs to slow down during the intensive image processing. The general principles of TFT operation should reflect this.
Image Data Formats
As stated previously, the DRAM Interface 81 is responsible for interfacing between other client portions of the ACP chip and the RAMBUS DRAM. In effect, each module within the DRAM Interface is an address generator.
There are three logical types of images manipulated by the ACP. They are:

    
    
        CCD Image, which is the Input Image captured from the CCD.
        Internal Image format—the Image format utilised internally by the Artcam device.
    
    


Print Image—the Output Image format printed by the Artcam
These images are typically different in color space, resolution, and the output & input color spaces which can vary from camera to camera. For example, a CCD image on a low-end camera may be a different resolution, or have different color characteristics from that used in a high-end camera. However all internal image formats are the same format in terms of color space across all cameras.
In addition, the three image types can vary with respect to which direction is ‘up’. The physical orientation of the camera causes the notion of a portrait or landscape image, and this must be maintained throughout processing. For this reason, the internal image is always oriented correctly, and rotation is performed on images obtained from the CCD and during the print operation.
CCD Image Organization
Although many different CCD image sensors could be utilised, it will be assumed that the CCD itself is a 750×500 image sensor, yielding 375,000 bytes (8 bits per pixel). Each 2×2 pixel block having the configuration as depicted in FIG. 30.
A CCD Image as stored in DRAM has consecutive pixels with a given line contiguous in memory. Each line is stored one after the other. The image sensor Interface 83 is responsible for taking data from the CCD and storing it in the DRAM correctly oriented. Thus a CCD image with rotation 0 degrees has its first line G, R, G, R, G, R . . . and its second line as B, G, B, G, B, G . . . . If the CCD image should be portrait, rotated 90 degrees, the first line will be R, G, R, G, R, G and the second line G, B, G, B, G, B . . . etc.
Pixels are stored in an interleaved fashion since all color components are required in order to convert to the internal image format.
It should be noted that the ACP 31 makes no assumptions about the CCD pixel format, since the actual CCDs for imaging may vary from Artcam to Artcam, and over time. All processing that takes place via the hardware is controlled by major microcode in an attempt to extend the usefulness of the ACP 31.
Internal Image Organization
Internal images typically consist of a number of channels. Vark images can include, but are not limited to:

    
    
        Lab
        Labα
        LabΔ
        αΔ
        L
        L, a and b correspond to components of the Lab color space, α is a matte channel (used for compositing), and Δ is a bump-map channel (used during brushing, tiling and illuminating).
    
    


The VLIW processor 74 requires images to be organized in a planar configuration. Thus a Lab image would be stored as 3 separate blocks of memory:
one block for the L channel,
one block for the a channel, and
one block for the b channel
Within each channel block, pixels are stored contiguously for a given row (plus some optional padding bytes), and rows are stored one after the other.
Turning to FIG. 31 there is illustrated an example form of storage of a logical image 100. The logical image 100 is stored in a planar fashion having L 101, a 102 and b 103 color components stored one after another. Alternatively, the logical image 100 can be stored in a compressed format having an uncompressed L component 101 and compressed A and B components 105, 106.
Turning to FIG. 32, the pixels of for line n 110 are stored together before the pixels of for line and n+1 (111). With the image being stored in contiguous memory within a single channel.
In the 8 MB-memory model, the final Print Image after all processing is finished, needs to be compressed in the chrominance channels. Compression of chrominance channels can be 4:1, causing an overall compression of 12:6, or 2:1.
Other than the final Print Image, images in the Artcam are typically not compressed. Because of memory constraints, software may choose to compress the final Print Image in the chrominance channels by scaling each of these channels by 2:1. If this has been done, the PRINT Vark function call utilised to print an image must be told to treat the specified chrominance channels as compressed. The PRINT function is the only function that knows how to deal with compressed chrominance, and even so, it only deals with a fixed 2:1 compression ratio.
Although it is possible to compress an image and then operate on the compressed image to create the final print image, it is not recommended due to a loss in resolution. In addition, an image should only be compressed once—as the final stage before printout. While one compression is virtually undetectable, multiple compressions may cause substantial image degradation.
Clip Image Organization
Clip images stored on Artcards have no explicit support by the ACP 31. Software is responsible for taking any images from the current Artcard and organizing the data into a form known by the ACP. If images are stored compressed on an Artcard, software is responsible for decompressing them, as there is no specific hardware support for decompression of Artcard images.
Image Pyramid Organization
During brushing, tiling, and warping processes utilised to manipulate an image it is often necessary to compute the average color of a particular area in an image. Rather than calculate the value for each area given, these functions make use of an image pyramid. As illustrated in FIG. 33, an image pyramid is effectively a multi-resolution pixel-map. The original image 115 is a 1:1 representation. Low-pass filtering and sub-sampling by 2:1 in each dimension produces an image 1⁄4 the original size 116. This process continues until the entire image is represented by a single pixel. An image pyramid is constructed from an original internal format image, and consumes 1⁄3 of the size taken up by the original image (1⁄4+ 1/16+ 1/64+ . . . ). For an original image of 1500×1000 the corresponding image pyramid is approximately 1⁄2MB. An image pyramid is constructed by a specific Vark function, and is used as a parameter to other Vark functions.
Print Image Organization
The entire processed image is required at the same time in order to print it. However the Print Image output can comprise a CMY dithered image and is only a transient image format, used within the Print Image functionality. However, it should be noted that color conversion will need to take place from the internal color space to the print color space. In addition, color conversion can be tuned to be different for different print rolls in the camera with different ink characteristics e.g. Sepia output can be accomplished by using a specific sepia toning Artcard, or by using a sepia tone print-roll (so all Artcards will work in sepia tone).
Color Spaces
As noted previously there are 3 color spaces used in the Artcam, corresponding to the different image types.
The ACP has no direct knowledge of specific color spaces. Instead, it relies on client color space conversion tables to convert between CCD, internal, and printer color spaces:
CCD:RGB
Internal:Lab
Printer:CMY
Removing the color space conversion from the ACP 31 allows:

    
    
        Different CCDs to be used in different cameras
        Different inks (in different print rolls over time) to be used in the same camera
        Separation of CCD selection from ACP design path
        A well defined internal color space for accurate color processing

Print Head 44

    
    


FIG. 34 illustrates the logical layout of a single print Head which logically consists of 8 segments, each printing bi-level cyan, magenta, and yellow onto a portion of the page.
Loading a Segment for Printing
Before anything can be printed, each of the 8 segments in the Print Head must be loaded with 6 rows of data corresponding to the following relative rows in the final output image:
Row 0=Line N, Yellow, even dots 0, 2, 4, 6, 8, . . . .
Row 1=Line N+8, Yellow, odd dots 1, 3, 5, 7, . . . .
Row 2=Line N+10, Magenta, even dots 0, 2, 4, 6, 8, . . . .
Row 3=Line N+18, Magenta, odd dots 1, 3, 5, 7, . . . .
Row 4=Line N+20, Cyan, even dots 0, 2, 4, 6, 8, . . . .
Row 5=Line N+28, Cyan, odd dots 1, 3, 5, 7, . . . .
Each of the segments prints dots over different parts of the page. Each segment prints 750 dots of one color, 375 even dots on one row, and 375 odd dots on another. The 8 segments have dots corresponding to positions:












Segment
First dot
Last dot

















0
0
749


1
750
1499


2
1500
2249


3
2250
2999


4
3000
3749


5
3750
4499


6
4500
5249


7
5250
5999









Each dot is represented in the Print Head segment by a single bit. The data must be loaded 1 bit at a time by placing the data on the segment's BitValue pin, and clocked in to a shift register in the segment according to a BitClock. Since the data is loaded into a shift register, the order of loading bits must be correct. Data can be clocked in to the Print Head at a maximum rate of 10 MHz.
Once all the bits have been loaded, they must be transferred in parallel to the Print Head output buffer, ready for printing. The transfer is accomplished by a single pulse on the segment's ParallelXferClock pin.
Controlling the Print
In order to conserve power, not all the dots of the Print Head have to be printed simultaneously. A set of control lines enables the printing of specific dots. An external controller, such as the ACP, can change the number of dots printed at once, as well as the duration of the print pulse in accordance with speed and/or power requirements.
Each segment has 5 NozzleSelect lines, which are decoded to select 32 sets of nozzles per row. Since each row has 375 nozzles, each set contains 12 nozzles. There are also 2 BankEnable lines, one for each of the odd and even rows of color. Finally, each segment has 3 ColorEnable lines, one for each of C, M, and Y colors. A pulse on one of the ColorEnable lines causes the specified nozzles of the color's specified rows to be printed. A pulse is typically about 2□s in duration.
If all the segments are controlled by the same set of NozzleSelect, BankEnable and ColorEnable lines (wired externally to the print head), the following is true:
If both odd and even banks print simultaneously (both BankEnable bits are set), 24 nozzles fire simultaneously per segment, 192 nozzles in all, consuming 5.7 Watts.
If odd and even banks print independently, only 12 nozzles fire simultaneously per segment, 96 in all, consuming 2.85 Watts.
Print Head Interface 62
The Print Head Interface 62 connects the ACP to the Print Head, providing both data and appropriate signals to the external Print Head. The Print Head Interface 62 works in conjunction with both a VLIW processor 74 and a software algorithm running on the CPU in order to print a photo in approximately 2 seconds.
An overview of the inputs and outputs to the Print Head Interface is shown in FIG. 35. The Address and Data Buses are used by the CPU to address the various registers in the Print Head Interface. A single BitClock output line connects to all 8 segments on the print head. The 8 DataBits lines lead one to each segment, and are clocked in to the 8 segments on the print head simultaneously (on a BitClock pulse). For example, dot 0 is transferred to segment0, dot 750 is transferred to segment, dot 1500 to segment2 etc. simultaneously.
The VLIW Output FIFO contains the dithered bi-level C, M, and Y 6000×9000 resolution print image in the correct order for output to the 8 DataBits. The ParallelXferClock is connected to each of the 8 segments on the print head, so that on a single pulse, all segments transfer their bits at the same time. Finally, the NozzleSelect, BankEnable and ColorEnable lines are connected to each of the 8 segments, allowing the Print Head Interface to control the duration of the C, M, and Y drop pulses as well as how many drops are printed with each pulse. Registers in the Print Head Interface allow the specification of pulse durations between 0 and 6 μs, with a typical duration of 2 μs.
Printing an Image
There are 2 phases that must occur before an image is in the hand of the Artcam user:
1. Preparation of the image to be printed
2. Printing the prepared image
Preparation of an image only needs to be performed once. Printing the image can be performed as many times as desired.
Prepare the Image
Preparing an image for printing involves:
1. Convert the Photo Image into a Print Image
2. Rotation of the Print Image (internal color space) to align the output for the orientation of the printer
3. Up-interpolation of compressed channels (if necessary)
4. Color conversion from the internal color space to the CMY color space appropriate to the specific printer and ink
At the end of image preparation, a 4.5 MB correctly oriented 1000×1500 CMY image is ready to be printed.
Convert Photo Image to Print Image
The conversion of a Photo Image into a Print Image requires the execution of a Vark script to perform image processing. The script is either a default image enhancement script or a Vark script taken from the currently inserted Artcard. The Vark script is executed via the CPU, accelerated by functions performed by the VLIW Vector Processor.
Rotate the Print Image
The image in memory is originally oriented to be top upwards. This allows for straightforward Vark processing. Before the image is printed, it must be aligned with the print roll's orientation. The re-alignment only needs to be done once. Subsequent Prints of a Print Image will already have been rotated appropriately.
The transformation to be applied is simply the inverse of that applied during capture from the CCD when the user pressed the “Image Capture” button on the Artcam. If the original rotation was 0, then no transformation needs to take place. If the original rotation was +90 degrees, then the rotation before printing needs to be −90 degrees (same as 270 degrees). The method used to apply the rotation is the Vark accelerated Affine Transform function. The Affine Transform engine can be called to rotate each color channel independently. Note that the color channels cannot be rotated in place. Instead, they can make use of the space previously used for the expanded single channel (1.5 MB).
FIG. 36 shows an example of rotation of a Lab image where the a and b channels are compressed 4:1. The L channel is rotated into the space no longer required (the single channel area), then the a channel can be rotated into the space left vacant by L, and finally the b channel can be rotated. The total time to rotate the 3 channels is 0.09 seconds. It is an acceptable period of time to elapse before the first print image. Subsequent prints do not incur this overhead.
Up Interpolate and Color Convert
The Lab image must be converted to CMY before printing. Different processing occurs depending on whether the a and b channels of the Lab image is compressed. If the Lab image is compressed, the a and b channels must be decompressed before the color conversion occurs. If the Lab image is not compressed, the color conversion is the only necessary step. The Lab image must be up interpolated (if the a and b channels are compressed) and converted into a CMY image. A single VLIW process combining scale and color transform can be used.
The method used to perform the color conversion is the Vark accelerated Color Convert function. The Affine Transform engine can be called to rotate each color channel independently. The color channels cannot be rotated in place. Instead, they can make use of the space previously used for the expanded single channel (1.5 MB).
Print the Image
Printing an image is concerned with taking a correctly oriented 1000×1500 CMY image, and generating data and signals to be sent to the external Print Head. The process involves the CPU working in conjunction with a VLIW process and the Print Head Interface.
The resolution of the image in the Artcam is 1000×1500. The printed image has a resolution of 6000×9000 dots, which makes for a very straightforward relationship: 1 pixel=6×6=36 dots. As shown in FIG. 37 since each dot is 16.6 μm, the 6×6 dot square is 100 μm square. Since each of the dots is bi-level, the output must be dithered.
The image should be printed in approximately 2 seconds. For 9000 rows of dots this implies a time of 222 μs time between printing each row. The Print Head Interface must generate the 6000 dots in this time, an average of 37 ns per dot. However, each dot comprises 3 colors, so the Print Head Interface must generate each color component in approximately 12 ns, or 1 clock cycle of the ACP (10 ns at 100 MHz). One VLIW process is responsible for calculating the next line of 6000 dots to be printed. The odd and even C, M, and Y dots are generated by dithering input from 6 different 1000×1500 CMY image lines. The second VLIW process is responsible for taking the previously calculated line of 6000 dots, and correctly generating the 8 bits of data for the 8 segments to be transferred by the Print Head Interface to the Print Head in a single transfer.
A CPU process updates registers in the first VLIW process 3 times per print line (once per color component=27000 times in 2 seconds0, and in the 2nd VLIW process once every print line (9000 times in 2 seconds). The CPU works one line ahead of the VLIW process in order to do this.
Finally, the Print Head Interface takes the 8 bit data from the VLIW Output FIFO, and outputs it unchanged to the Print Head, producing the BitClock signals appropriately. Once all the data has been transferred a ParallelXferClock signal is generated to load the data for the next print line. In conjunction with transferring the data to the Print Head, a separate timer is generating the signals for the different print cycles of the Print Head using the NozzleSelect, ColorEnable, and BankEnable lines a specified by Print Head Interface internal registers.
The CPU also controls the various motors and guillotine via the parallel interface during the print process.
Generate C, M, and Y Dots
The input to this process is a 1000×1500 CMY image correctly oriented for printing. The image is not compressed in any way. As illustrated in FIG. 38, a VLIW microcode program takes the CMY image, and generates the C, M, and Y pixels required by the Print Head Interface to be dithered.
The process is run 3 times, once for each of the 3 color components. The process consists of 2 sub-processes run in parallel—one for producing even dots, and the other for producing odd dots. Each sub-process takes one pixel from the input image, and produces 3 output dots (since one pixel=6 output dots, and each sub-process is concerned with either even or odd dots). Thus one output dot is generated each cycle, but an input pixel is only read once every 3 cycles.
The original dither cell is a 64×64 cell, with each entry 8 bits. This original cell is divided into an odd cell and an even cell, so that each is still 64 high, but only 32 entries wide. The even dither cell contains original dither cell pixels 0, 2, 4 etc., while the odd contains original dither cell pixels 1, 3, 5 etc. Since a dither cell repeats across a line, a single 32 byte line of each of the 2 dither cells is required during an entire line, and can therefore be completely cached. The odd and even lines of a single process line are staggered 8 dot lines apart, so it is convenient to rotate the odd dither cell's lines by 8 lines. Therefore the same offset into both odd and even dither cells can be used. Consequently the even dither cell's line corresponds to the even entries of line L in the original dither cell, and the even dither cell's line corresponds to the odd entries of line L+8 in the original dither cell.
The process is run 3 times, once for each of the color components. The CPU software routine must ensure that the Sequential Read Iterators for odd and even lines are pointing to the correct image lines corresponding to the print heads. For example, to produce one set of 18,000 dots (3 sets of 6000 dots):
Yellow even dot line=0, therefore input Yellow image line=0/6=0
Yellow odd dot line=8, therefore input Yellow image line=8/6=1
Magenta even line=10, therefore input Magenta image line=10/6=1
Magenta odd line=18, therefore input Magenta image line=18/6=3
Cyan even line=20, therefore input Cyan image line=20/6=3
Cyan odd line=28, therefore input Cyan image line=28/6=4
Subsequent sets of input image lines are:
Y=[0, 1], M=[1, 3], C=[3, 4]
Y=[0, 1], M=[1, 3], C=[3, 4]
Y=[0, 1], M=[2, 3], C=[3, 5]
Y=[0, 1], M=[2, 3], C=[3, 5]
Y=[0, 2], M=[2, 3], C=[4, 5]
The dither cell data however, does not need to be updated for each color component. The dither cell for the 3 colors becomes the same, but offset by 2 dot lines for each component.
The Dithered Output is written to a Sequential Write Iterator, with odd and even dithered dots written to 2 separate outputs. The same two Write Iterators are used for all 3 color components, so that they are contiguous within the break-up of odd and even dots.
While one set of dots is being generated for a print line, the previously generated set of dots is being merged by a second VLIW process as described in the next section.
Generate Merged 8 Bit Dot Output
This process, as illustrated in FIG. 39, takes a single line of dithered dots and generates the 8 bit data stream for output to the Print Head Interface via the VLIW Output FIFO. The process requires the entire line to have been prepared, since it requires semi-random access to most of the dithered line at once. The following constant is set by software:














Constant
Value









K1
375










The Sequential Read Iterators point to the line of previously generated dots, with the Iterator registers set up to limit access to a single color component. The distance between subsequent pixels is 375, and the distance between one line and the next is given to be 1 byte. Consequently 8 entries are read for each “line”. A single “line” corresponds to the 8 bits to be loaded on the print head. The total number of “lines” in the image is set to be 375. With at least 8 cache lines assigned to the Sequential Read Iterator, complete cache coherence is maintained. Instead of counting the 8 bits, 8 Microcode steps count implicitly.
The generation process first reads all the entries from the even dots, combining 8 entries into a single byte which is then output to the VLIW Output FIFO. Once all 3000 even dots have been read, the 3000 odd dots are read and processed. A software routine must update the address of the dots in the odd and even Sequential Read Iterators once per color component, which equates to 3 times per line. The two VLIW processes require all 8 ALUs and the VLIW Output FIFO. As long as the CPU is able to update the registers as described in the two processes, the VLIW processor can generate the dithered image dots fast enough to keep up with the printer.
Data Card Reader
FIG. 40, there is illustrated on form of card reader 500 which allows for the insertion of Artcards 9 for reading. FIG. 39 shows an exploded perspective of the reader of FIG. 40. Cardreader is interconnected to a computer system and includes a CCD reading mechanism 35. The cardreader includes pinch rollers 506, 507 for pinching an inserted Artcard 9. One of the roller e.g. 506 is driven by an Artcard motor 37 for the advancement of the card 9 between the two rollers 506 and 507 at a uniformed speed. The Artcard 9 is passed over a series of LED lights 512 which are encased within a clear plastic mould 514 having a semi circular cross section. The cross section focuses the light from the LEDs eg 512 onto the surface of the card 9 as it passes by the LEDs 512. From the surface it is reflected to a high resolution linear CCD 34 which is constructed to a resolution of approximately 480 dpi. The surface of the Artcard 9 is encoded to the level of approximately 1600 dpi hence, the linear CCD 34 supersamples the Artcard surface with an approximately three times multiplier. The Artcard 9 is further driven at a speed such that the linear CCD 34 is able to supersample in the direction of Artcard movement at a rate of approximately 4800 readings per inch. The scanned Artcard CCD data is forwarded from the Artcard reader to ACP 31 for processing. A sensor 49, which can comprise a light sensor acts to detect of the presence of the card 13.
The CCD reader includes a bottom substrate 516, a top substrate 514 which comprises a transparent molded plastic. In between the two substrates is inserted the linear CCD array 34 which comprises a thin long linear CCD array constructed by means of semi-conductor manufacturing processes.
Turning to FIG. 41, there is illustrated a side perspective view, partly in section, of an example construction of the CCD reader unit. The series of LEDs eg. 512 are operated to emit light when a card 9 is passing across the surface of the CCD reader 34. The emitted light is transmitted through a portion of the top substrate 523. The substrate includes a portion eg. 529 having a curved circumference so as to focus light emitted from LED 512 to a point eg. 532 on the surface of the card 9. The focused light is reflected from the point 532 towards the CCD array 34. A series of microlenses eg. 534, shown in exaggerated form, are formed on the surface of the top substrate 523. The microlenses 523 act to focus light received across the surface to the focused down to a point 536 which corresponds to point on the surface of the CCD reader 34 for sensing of light falling on the light sensing portion of the CCD array 34.
A number of refinements of the above arrangement are possible. For example, the sensing devices on the linear CCD 34 may be staggered. The corresponding microlenses 34 can also be correspondingly formed as to focus light into a staggered series of spots so as to correspond to the staggered CCD sensors.
To assist reading, the data surface area of the Artcard 9 is modulated with a checkerboard pattern as previously discussed with reference to FIG. 39. Other forms of high frequency modulation may be possible however.
It will be evident that an Artcard printer can be provided as for the printing out of data on storage Artcard. Hence, the Artcard system can be utilized as a general form of information distribution outside of the Artcam device. An Artcard printer can prints out Artcards on high quality print surfaces and multiple Artcards can be printed on same sheets and later separated. On a second surface of the Artcard 9 can be printed information relating to the files etc. stored on the Artcard 9 for subsequent storage.
Hence, the Artcard system allows for a simplified form of storage which is suitable for use in place of other forms of storage such as CD ROMs, magnetic disks etc. The Artcards 9 can also be mass produced and thereby produced in a substantially inexpensive form for redistribution.
Print Rolls
Turning to FIG. 43, there is illustrated the print roll 42 and print-head portions of the Artcam. The paper/film 611 is fed in a continuous “web-like” process to a printing mechanism 15 which includes further pinch rollers 616-619 and a print head 44
The pinch roller 613 is connected to a drive mechanism (not shown) and upon rotation of the print roller 613, “paper” in the form of film 611 is forced through the printing mechanism 615 and out of the picture output slot 6. A rotary guillotine mechanism (not shown) is utilised to cut the roll of paper 611 at required photo sizes.
It is therefore evident that the printer roll 42 is responsible for supplying “paper” 611 to the print mechanism 615 for printing of photographically imaged pictures.
In FIG. 44, there is shown an exploded perspective of the print roll 42. The printer roll 42 includes output printer paper 611 which is output under the operation of pinching rollers 612, 613.
Referring now to FIG. 45, there is illustrated a more fully exploded perspective view, of the print roll 42 of FIG. 44 without the “paper” film roll. The print roll 42 includes three main parts comprising ink reservoir section 620, paper roll sections 622, 623 and outer casing sections 626, 627.
Turning first to the ink reservoir section 620, which includes the ink reservoir or ink supply sections 633. The ink for printing is contained within three bladder type containers 630-632. The printer roll 42 is assumed to provide full color output inks. Hence, a first ink reservoir or bladder container 630 contains cyan colored ink. A second reservoir 631 contains magenta colored ink and a third reservoir 632 contains yellow ink. Each of the reservoirs 630-632, although having different volumetric dimensions, are designed to have substantially the same volumetric size.
The ink reservoir sections 621, 633, in addition to cover 624 can be made of plastic sections and are designed to be mated together by means of heat sealing, ultra violet radiation, etc. Each of the equally sized ink reservoirs 630-632 is connected to a corresponding ink channel 639-641 for allowing the flow of ink from the reservoir 630-632 to a corresponding ink output port 635-637. The ink reservoir 632 having ink channel 641, and output port 637, the ink reservoir 631 having ink channel 640 and output port 636, and the ink reservoir 630 having ink channel 639 and output port 637.
In operation, the ink reservoirs 630-632 can be filled with corresponding ink and the section 633 joined to the section 621. The ink reservoir sections 630-632, being collapsible bladders, allow for ink to traverse ink channels 639-641 and therefore be in fluid communication with the ink output ports 635-637. Further, if required, an air inlet port can also be provided to allow the pressure associated with ink channel reservoirs 630-632 to be maintained as required.
The cap 624 can be joined to the ink reservoir section 620 so as to form a pressurized cavity, accessible by the air pressure inlet port.
The ink reservoir sections 621, 633 and 624 are designed to be connected together as an integral unit and to be inserted inside printer roll sections 622, 623. The printer roll sections 622, 623 are designed to mate together by means of a snap fit by means of male portions 645-647 mating with corresponding female portions (not shown). Similarly, female portions 654-656 are designed to mate with corresponding male portions 660-662. The paper roll sections 622, 623 are therefore designed to be snapped together. One end of the film within the role is pinched between the two sections 622, 623 when they are joined together. The print film can then be rolled on the print roll sections 622, 625 as required.
As noted previously, the ink reservoir sections 620, 621, 633, 624 are designed to be inserted inside the paper roll sections 622, 623. The printer roll sections 622, 623 are able to be rotatable around stationery ink reservoir sections 621, 633 and 624 to dispense film on demand.
The outer casing sections 626 and 627 are further designed to be coupled around the print roller sections 622, 623. In addition to each end of pinch rollers eg 612, 613 is designed to clip in to a corresponding cavity eg 670 in cover 626, 627 with roller 613 being driven externally (not shown) to feed the print film and out of the print roll.
Finally, a cavity 677 can be provided in the ink reservoir sections 620, 621 for the insertion and gluing of an silicon chip integrated circuit type device 53 for the storage of information associated with the print roll 42.
As shown in FIG. 36 and FIG. 45, the print roll 42 is designed to be inserted into the Artcam camera device so as to couple with a coupling unit 680 which includes connector pads 681 for providing a connection with the silicon chip 53. Further, the connector 680 includes end connectors of four connecting with ink supply ports 635-637. The ink supply ports are in turn to connect to ink supply lines eg 682 which are in turn interconnected to printheads supply ports eg. 687 for the flow of ink to print-head 44 in accordance with requirements.
The “media” 611 utilised to form the roll can comprise many different materials on which it is designed to print suitable images. For example, opaque rollable plastic material may be utilized, transparencies may be used by using transparent plastic sheets, metallic printing can take place via utilization of a metallic sheet film. Further, fabrics could be utilised within the printer roll 42 for printing images on fabric, although care must be taken that only fabrics having a suitable stiffness or suitable backing material are utilised.
When the print media is plastic, it can be coated with a layer, which fixes and absorbs the ink. Further, several types of print media may be used, for example, opaque white matte, opaque white gloss, transparent film, frosted transparent film, lenticular array film for stereoscopic 3D prints, metallized film, film with the embossed optical variable devices such as gratings or holograms, media which is pre-printed on the reverse side, and media which includes a magnetic recording layer. When utilizing a metallic foil, the metallic foil can have a polymer base, coated with a thin (several micron) evaporated layer of aluminum or other metal and then coated with a clear protective layer adapted to receive the ink via the ink printer mechanism.
In use the print roll 42 is obviously designed to be inserted inside a camera device so as to provide ink and paper for the printing of images on demand. The ink output ports 635-637 meet with corresponding ports within the camera device and the pinch rollers 672, 673 are operated to allow the supply of paper to the camera device under the control of the camera device.
As illustrated in FIG. 45, a mounted silicon chip 53 is inserted in one end of the print roll 42. In FIG. 165 the authentication chip 53 is shown in more detail and includes four communications leads 680-683 for communicating details from the chip 53 to the corresponding camera to which it is inserted.
Turning to FIG. 165, the chip can be separately created by means of encasing a small integrated circuit 687 in epoxy and running bonding leads eg. 688 to the external communications leads 680-683. The integrated chip 687 being approximately 400 microns square with a 100 micron scribe boundary. Subsequently, the chip can be glued to an appropriate surface of the cavity of the print roll 42. In FIG. 166, there is illustrated the integrated circuit 687 interconnected to bonding pads 681, 682 in an exploded view of the arrangement of FIG. 165.
In FIGS. 45A to 45E of the drawings, reference numeral 1100 generally designates a print cartridge 1100. The print cartridge 1100 includes an ink cartridge 1102, in accordance with the invention.
The print cartridge 1100 includes a housing 1104. As illustrated more clearly in FIG. 2 of the drawings, the housing 1104 is defined by an upper molding 1106 and a lower molding 1108. The moldings 1106 and 1108 clip together by means of clips 1110. The housing 1104 is covered by a label 1112 which provides an attractive appearance to the cartridge 1100. The label 1112 also carries information to enable a user to use the cartridge 1100.
The housing 1104 defines a chamber 1114 in which the ink cartridge 1102 is received. The ink cartridge 1102 is fixedly supported in the chamber 1114 of the housing 1104.
A supply of print media 1116 comprising a roll 1126 of film/media 1118 wound about a former 1120 is received in the chamber 1114 of the housing 1104. The former 1120 is slidably received over the ink cartridge 1102 and is rotatable relative thereto.
As illustrated in FIG. 45B of the drawings, when the upper molding 1106 and lower molding 1108 are clipped together, an exit slot 1122 is defined through which a tongue of the paper 1118 is ejected.
The cartridge 1100 includes a roller assembly 1124 which serves to de-curl the paper 1118 as it is fed from the roll 1126 and also to drive the paper 1118 through the slot 1122. The roller assembly 1124 includes a drive roller 1128 and two driven rollers 1130. The driven rollers 1130 are rotatably supported in ribs 1132 which stand proud of a floor 1134 of the lower molding 1108 of the housing 1104. The rollers 1130, together with the drive roller 1128, provide positive traction to the paper 1118 to control its speed and position as it is ejected from the housing 1104. The rollers 1130 are injection moldings of a suitable synthetic plastics material such as polystyrene. In this regard also, the upper molding 1106 and the lower molding 1108 are injection moldings of suitable synthetic plastics material, such as polystyrene.
The drive roller 1128 includes a drive shaft 1136 which is held rotatably captive between mating recesses 1138 and 1140 defined in a side wall of each of the upper molding 1106 and the lower molding 1108, respectively, of the housing 1104. An opposed end 1142 of the drive roller 1128 is held rotatably in suitable formations (not shown) in the upper molding 1106 and the lower molding 1108 of the housing 1104.
The drive roller 1128 is a two shot injection molding comprising the shaft 1136 which is of a high impact polystyrene and on which are molded a bearing means in the form of elastomeric or rubber roller portions 1144. These portions 1144 positively engage the paper 1118 and inhibit slippage of the paper 1118 as the paper 1118 is fed from the cartridge 1100.
The end of the roller 1128 projecting from the housing 1104 has an engaging formation in the form of a cruciform arrangement 1146 (FIG. 45A) which mates with a geared drive interface (not shown) of a printhead assembly of a device, such as a camera, in which the print cartridge 1100 is installed. This arrangement ensures that the speed at which the paper 1118 is fed to the printhead is synchronised with printing by the printhead to ensure accurate registration of ink on the paper 1118.
The ink cartridge 1102 includes a container 1148 which is in the form of a right circular cylindrical extrusion. The container 1148 is extruded from a suitable synthetic plastics material such as polystyrene.
In a preferred embodiment of the invention, the printhead with which the print cartridge 1100 is used, is a multi-colored printhead. Accordingly, the container 1148 is divided into a plurality of, more particularly, four compartments or reservoirs 1150. Each reservoir 1150 houses a different color or type of ink. In one embodiment, the inks contained in the reservoirs 1150 are cyan, magenta, yellow and black inks. In another embodiment of the invention, three different colored inks, being cyan, magenta and yellow inks, are accommodated in three of the reservoirs 1150 while a fourth reservoir 1150 houses an ink which is visible in the infra-red light spectrum only.
As shown more clearly in FIGS. 45C and 45D of the drawings, one end of the container 1148 is closed off by an end cap 1152. The end cap 1152 has a plurality of openings 1154 defined in it. An opening 1154 is associated with each reservoir 1150 so that atmospheric pressure is maintained in the reservoir 1150 at that end of the container 1148 having the end cap 1152.
A seal arrangement 1156 is received in the container 1148 at the end having the end cap 1152. The seal arrangement 1156 comprises a quadrant shaped pellet 1158 of gelatinous material slidably received in each reservoir 1150. The gelatinous material of the pellet 1158 is a compound made of a thermoplastic rubber and a hydrocarbon. The hydrocarbon is a white mineral oil. The thermoplastic rubber is a copolymer which imparts sufficient rigidity to the mineral oil so that the pellet 1158 retains its form at normal operating temperatures while permitting sliding of the pellet 1158 within its associated reservoir 1150. A suitable thermoplastic rubber is that sold under the registered trademark of “Kraton” by the Shell Chemical Company. The copolymer is present in the compound in an amount sufficient to impart a gel-like consistency to each pellet 1158. Typically, the copolymer, depending on the type used, would be present in an amount of approximately three percent to twenty percent by mass.
In use, the compound is heated so that it becomes fluid. Once each reservoir 1150 has been charged with its particular type of ink, the compound, in a molten state, is poured into each reservoir 1150 where the compound is allowed to set to form the pellet 1158. Atmospheric pressure behind the pellets 1158, that is, at that end of the pellet 1158 facing the end cap 1152 ensures that, as ink is withdrawn from the reservoir 1150, the pellets 1158, which are self-lubricating, slide towards an opposed end of the container 1148. The pellets 1158 stop ink emptying out of the container when inverted, inhibit contamination of the ink in the reservoir 1150 and also inhibit drying out of the ink in the reservoir 1150. The pellets 1158 are hydrophobic further to inhibit leakage of ink from the reservoirs 1150.
The opposed end of the container 1148 is closed off by an ink collar molding 1160. Baffles 1162 carried on the molding 1160 receive an elastomeric seal molding 1164. The elastomeric seal molding 1164, which is hydrophobic, has sealing curtains 1166 defined therein. Each sealing curtain 1166 has a slit 1168 so that a mating pin (not shown) from the printhead assembly is insertable through the slits 1168 into fluid communication with the reservoirs 1150 of the container 1148. Hollow bosses 1170 project from an opposed side of the ink collar molding 1160. Each boss 1170 is shaped to fit snugly in its associated reservoir 1150 for locating the ink collar molding on the end of the container 1148.
Reverting again to FIG. 45C of the drawings, the ink collar molding 1160 is retained in place by means of a carrier or fascia molding 1172. The fascia molding 1172 has a four leaf clover shaped window 1174 defined therein through which the elastomeric seal molding 1164 is accessible. The fascia molding 1174 is held captive between the upper molding 1106 and the lower molding 1108 of the housing 1104. The fascia molding 1174 and webs 1176 and 1178 extending from an interior surface of the upper molding 1106 and the lower molding 1108 respectively, of the housing 1104 define a compartment 1180. An air filter 1182 is received in the compartment 1180 and is retained in place by the end molding 1174. The air filter 1182 cooperates with the printhead assembly. Air is blown across a nozzle guard of a printhead assembly to effect cleaning of the nozzle guard. This air is filtered by being drawn through the air filter 1182 by means of a pin (not shown) which is received in an inlet opening 1184 in the fascia molding 1172.
The air filter 1182 is shown in greater detail in FIG. 45E of the drawings. The air filter 1182 comprises a filter medium 1192. The filter medium 1192 is synthetic fiber based and is arranged in a fluted form to increase the surface area available for filtering purposes. Instead of a paper based filter medium 1192 other fibrous batts could also be used.
The filter medium 1192 is received in a canister 1194. The canister 1194 includes a base molding 1196 and a lid 1198. To be accommodated in the compartment 1180 of the housing 1104, the canister 1194 is part-annular or horse shoe shaped. Thus, the canister 1194 has a pair of opposed ends 1200. An air inlet opening 1202 is defined in each end 1200.
An air outlet opening 1204 is defined in the lid 1198. The air outlet opening 1204, initially, is closed off by a film or membrane 1206. When the filter 1182 is mounted in position in the compartment 1180, the air outlet opening 1204 is in register with the opening 1184 in the fascia molding 1172. The pin from the printhead assembly pierces the film 1206 then draws air from the atmosphere through the air filter 1182 prior to the air being blown over the nozzle guard and the printhead of the printhead assembly.
The base molding 1194 includes locating formations 1208 and 1210 for locating the filter medium 1192 in position in the canister 1194. The locating formations 1208 are in the form of a plurality of pins 1212 while the locating formations 1210 are in the form of ribs which engage ends 1214 of the filter medium 11192.
Once the filter medium 1192 has been placed in position in the base mold 1196, the lid 1198 is secured to the base molding 1196 by ultrasonic welding or similar means to seal the lid 1198 to the base molding 1196.
When the print cartridge 1100 has been assembled, a membrane or film 1186 is applied to an outer end of the fascia molding 1172 to close off the window 1174. This membrane or film 1186 is pierced or ruptured by the pins, for use. The film 1186 inhibits the ingress of detritus into the ink reservoirs 1150.
An authentication means in the form of an authentication chip 1188 is received in an opening 1190 in the fascia molding 1172. The authentication chip 1188 is interrogated by the printhead assembly 1188 to ensure that the print cartridge 1100 is compatible and compliant with the printhead assembly of the device.

## Claims

1. A microcontroller for an image sensing and processing apparatus, the microcontroller comprising:
VLIW processor circuitry;
image sensor interface circuitry connected between the VLIW processor circuitry and the image sensor;
bus interface circuitry connected between the VLIW processor circuitry and a bus connectable with devices other than the image sensor; and
buffer memory and queuing circuitry intermediate the VLIW processor and each of the image sensor and bus interface circuitry to control delivery of information to the VLIW processor.

2. A microcontroller as claimed in claim 1, in which the interface circuitry defines a state machine that is configured to provide the image sensor with control information generated by the VLIW processor.

3. A microcontroller as claimed in claim 1, in which the image sensor is in the form of a CMOS-based image sensor.

4. A microcontroller as claimed in claim 2, in which the image sensor is in the form of an active pixel sensor (APS).

5. A microcontroller as claimed in claim 1, in which the image sensor is in the form of a charge-coupled device (CCD) sensor.

6. A microcontroller as claimed in claim 1, in which the interface circuitry defines an analog/digital converter (ADC) to convert an analog signal generated by the image sensor into a digital signal and to convert a digital signal carrying control information generated by the VLIW processor into a suitable analog signal that is readable by the image sensor.