PATENT DOCUMENT

Abstract:
An information processing device is disclosed. The information processing device includes a heal dissipation plate structure including a thermally conductive material, and a processor including a major surface. A heat dissipating material is between and couples the processor and the heat dissipation plate structure. An array of pins is substantially perpendicular to the major surface of the processor. The device also includes a substrate including a plurality of holes, where the pins in the array of pins are configured to be inserted into the holes in the substrate.

Full Description:
CONTINUING APPLICATION DATA 
   This is a continuation application of prior application Ser. No. 10/727,400, filed Dec. 3, 2003, now U.S. Pat. No. 6,845,014, which is a continuation of Ser. No. 10/442,873, filed May 21, 2003, now U.S. Pat. No. 6,771,509, which is a continuation of Ser. No. 10/315,781, now U.S. Pat. No. 6,608,753, filed on Dec. 10, 2002, which is a continuation of Ser. No. 10/128,731, filed on Apr. 24, 2002 now U.S. Pat. No. 6,515,864, which is a continuation of Ser. No. 09/452,625, filed on Dec. 1, 1999, issued as U.S. Pat. No. 6,404,639 which is a continuation of Ser. No. 08/866,195, filed on May 30, 1997, issued as U.S. Pat. No. 6,025,993, which is a continuation of Ser. No. 08/439,633, filed on May 12, 1995, issued as U.S. Pat. No. 5,659,459, which is a continuation of Ser. No. 08/026,902 filed on Mar. 5, 1993 which is now abandoned, the contents of such applications and patents are incorporated herein by reference in their entirety for all purposes. 

   CROSS REFERENCES TO RELATED APPLICATIONS 
   This application is also related to the following other applications: 
   “INTELLIGENT CARTRIDGE FOR ATTACHMENT TO A PRINTER TO PERFORM IMAGE PROCESSING TASKS IN A COMBINATION IMAGE PROCESSING SYSTEM AND METHOD OF IMAGE PROCESSING”, Wakabayashi et al., Ser. No. 07/816,455, filed Dec. 30, 1991 (P16491a), issued as U.S. Pat. No. 5,410,641. 
   “INFORMATION PROCESSING DEVICE IN AN ELECTRONIC APPARATUS UTILIZING AN ACCESSORY CONTROL DEVICE AND METHODS OF APPLICATION”, Wakabayashi et al., Ser. No. 07/883,753, filed May 15, 1992 (P16655a), issued as U.S. Pat. No. 5,461,705. 
   “INFORMATION PROCESSING DEVICE IN AN ELECTRONIC APPARATUS UTILIZING AN ACCESSORY CONTROL DEVICE AND METHODS OF APPLICATION”, Wakabayashi et al., Ser. No. 07/895,537 (P16646a), filed Jun. 8, 1992, which is now abandoned. 
   “APPARATUS TYPE IDENTIFICATION DEVICE AND METHOD THEREFOR”, Wakabayashi et al., Ser. No. 07/908,671 (P16619a), filed Jul. 2, 1992, which is now abandoned. 
   “INFORMATION PROCESSING DEVICE AND THE ACCESSORY CONTROL DEVICE AND INFORMATION PROCESSING METHOD IT USES”, Wakabayashi et al., Ser. No. 07/910,590 P16628a), filed Jul. 8, 1992, issued as U.S. Pat. No. 5,553,202. 
   “ADD-ON ELECTRONIC DEVICE AND ELECTRONIC SYSTEM”, Wakabayashi et al., Ser. No. 07/854,643 (P16637a), filed Jul. 1, 1992, issued as U.S. Pat. No. 5,437,041. 
   “INFORMATION PROCESSING DEVICE AND THE ACCESSORY CONTROL DEVICE AND INFORMATION PROCESSING METHOD IT USES”, Wakabayashi et al., Ser. No. 07/910,851 (P16664a), filed Jul. 7, 1992, issued as U.S. Pat. No. 5,461,704. 
   “TEMPERATURE CONTROL FOR ADD-ON ELECTRONIC DEVICES”, Wakabayashi et al., Ser. No. 07/907,988 (P16673a), filed Jul. 1, 1992, issued as U.S. Pat. No. 5,526,229. 
   “INFORMATION PROCESSING DEVICE AND THE ACCESSORY CONTROL DEVICE AND INFORMATION PROCESSING METHOD IT USES”, Wakabayashi et al., Ser. No. 07/911,558 (P16682a), filed Jul. 7, 1992, issued as U.S. Pat. No. 5,504,669. 
   The applications listed above are incorporated herein by reference thereto. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to plug in type cartridges for providing additional or new operating features for printers and other existing electronic systems, and more particularly to a method and apparatus for minimizing extraneous electromagnetic noise generated by such cartridge devices. 
   2. Description of the Related Art 
   In recent years, digital electronic equipment, such as, personal computers, word processors, work stations, and other electronic equipment using built-in microprocessors, such as printers, facsimile machines, memo devices, musical instruments, cooking equipment, and cameras, has found extensive use throughout large segments of society. In addition, other widely used apparatus such as automobiles, robots, numerically controlled machines, and a variety of other electrified products, now make use of microprocessor technology. 
   The application of programmable digital logic to equipment operation makes more flexible control possible compared to that obtained with simple feedback controls previously used with various fixed hardware designs. In addition, using programmable logic, essential operating functions are easily altered by simply changing command software. One advantage of this approach is that totally different control operations are obtainable for a given piece of equipment or hardware by simply modifying the contents of program storage or memory elements, such as ROMs, that store specific processing or program steps. Moreover, smaller incremental changes in function, such as occur for design revisions, can be advantageously implemented by only upgrading software. 
   However, the ultimate capabilities of processor controlled electronic equipment are determined by the capabilities of the processor itself. That is, each processor is itself finally limited by operating characteristics such as the maximum number of processing steps obtainable per unit time, the maximum number of data bits that can be processed at one time, the width of any data or command transfer buses, and so forth. As a result of these limitations, achieving improvements by merely upgrading software versions is at best limited to improving equipment ease of use. Realistically, it has not been possible to achieve significant improvements in operating functionality for existing electronic equipment. 
   At the same time, improving or upgrading software versions often requires replacing a ROM or other memory element in which the software is “burned” or contained. It is much more difficult to obtain access to or change software when replacement of such code containing ROMs is required. As a result, revising software to improve equipment operation is actually very difficult unless the particular piece of electronic equipment is already scheduled for a ROM exchange, different ROM version, at the time of its initial design, or unless the software can be supplied on a replaceable medium such as a flexible disk and used to modify stored program material. 
   For some applications, devices called “accelerators” are used to improve overall equipment function, operability, or capabilities by completely replacing key control components such as microprocessors which otherwise impose limits on operation. This type of hardware “upgrade” is commonly encountered with personal computers. However, this approach requires replacing components, a microprocessor, generally located on a motherboard within the apparatus, and represents a task that is beyond the skill of most equipment users. Furthermore, for typical consumer electronic equipment such as the previously mentioned printers, facsimile machines, musical instruments, cooking equipment, cameras, automobiles, etc., absolutely no consideration is commonly given to providing for such improvements or upgrading functionality and no such hardware option exists. A good example of this lack of planning is seen in relation to page printers which are manufactured for use with computers. 
   In recent years, page printers, such as laser printers, have enjoyed widespread distribution and are rapidly becoming the common, leading, device for high-speed data and image output from computers. The resolution of laser printers typically ranges from 240 to 800 dots per inch (dpi), and printing speed is on the order of several pages a minute. Such printers principally employ an electrophotographic printer element, such as a xerography unit, which uses a photo-sensitive drum as part of the printing engine. After the printer has received and stored one page of image data (or blank), image processing steps, that is, electrostatic charge, exposure, toner application, and image transfer, take place continuously in synchronization with rotation of the photo-sensitive drum. 
   Therefore, page printer memory capacity for image development or processing must be sufficient to store at least one page of image data at a time. If no image data compression is employed, this capacity is determined by the printer resolution being used and the page size to be accommodated. For example, if a resolution of 300 dpi and a page size of 8 by 10 inches are used, the printer may handle as much as 8×300×10×300 or 7,200,000 dots or pixels, of image data. If the print or image input data is in the form of a bit mapped image, the printer only needs to accept and sequentially store this data before image processing. The processing speed for this type of operation generally depends on, and is limited by, the data transfer rate. Since parallel data transfer, such as that complying with the Centronics specification standard, occurs at a considerably high rate, it is unlikely that data transfer of bit images will occur at a slower rate than the printing capability of the xerographic unit. 
   However, where printers receive and process other types of data, such as character codes, line positions, and line and character pitch, and then develop this data into a page image, or receive programs that describe the page using a page description language (PDL) and then interpret and process this information to generate a page image, it is necessary to perform arithmetic processing and generation of bit mapped images from the input print data. In comparison to directly transferring a simple bit image, the extra image processing overhead incurred by such processing imposes a major reduction in overall printing speed. That is, the image output speed of the printer is now substantially determined, or limited, by the speed with which the processor performs image processing and memory accesses which combine to create much slower transfer rates than the xerography unit is capable of handling, resulting in a major reduction in printing capability. 
   For example, in a page printer capable of printing ten pages a minute, no more than six seconds are allowed for processing image data for each page to be printed. Processing 0.9 megabytes of stored data into an image within this time span only provides for 6.67 microseconds of processing time per byte of data (6 seconds divided by 0.9 megabytes). Such short processing periods represent a processing capacity that may or may not be realizable even with currently available high-speed RISC type processors. In contrast to this processing limitation, the electrostatic image and photosensitive elements of a laser printer are often capable of easily printing ten or more pages per minute. As a result, under the current state of the art, the processing capability of a printer image data control unit represents a major bottleneck in improving overall printing speed. 
   Many page printers are provided with either an internal memory expansion capability or an expansion slot to provide some additional processing capacity. Where an expansion slot is provided, insertion of an “add-on” or expansion “cartridge”, containing font information or a program, expands printer functionality. The addition of pre-formed fonts and font control language to the printer may speed image formation by alleviating the need for some image processing steps. However, even if processing speed is increased using some form of memory expansion, it is not possible to improve the processor performance itself or data throughput. For example, for a laser printer only supporting one particular PDL, PDL interpreter programs are typically available in the form of integrated circuit cards and add-on cartridges for expanding processing functions to accommodate other page description languages. Such cartridges store programs, or special program routines, typically in mask ROM form for recall during image processing, and are inserted into the expansion slot of the printer. But the basic printer processor is unchanged and may even run slower implementing these routines. 
   Expansion cartridge slots have a specific address, or address range or space assigned to them which is detected and read by a printer control unit after power is applied to the printer. If a cartridge containing a PDL interpreter program has been inserted, and, therefore, resides at the appropriate addresses, a pre-selected code is returned to the controller to indicate that the cartridge contains a PDL program. In this situation, control of the printer for image data developing switches to the interpreter program which is read from its address locations inside the cartridge. As a result, the printer is able to interpret received data based on the use of the particular PDL implemented by the cartridge program. The use of an interpreter program does not itself increase the processing speed and the overall printing speed may in fact decrease as a result of employing a high level description language with the printer processor. 
   For this and other reasons, a cartridge equipped with a second microprocessor separate from that normally used by the main printer has been invented to resolve the problems described above. This cartridge and certain of its features are disclosed in the co-pending U.S. patent applications listed above which are incorporated herein by reference. The disclosed cartridge is able to receive print data from the printer and use its own microprocessor to process and develop image data based on stored PDL interpreters and other program data, and then provide print data back to the printer for forming the desired output image. 
   The operation of this type of cartridge creates potential problems regarding heat radiation and accumulation. Any advanced microprocessor used in the cartridge comprises an electronic circuit having from tens to hundreds of thousands of components or elements, such as transistors, which operate, or switch between operating states, at frequencies of 20 MHz to 40 MHz, or higher. As a consequence, such microprocessors typically generate substantial amounts of heat during operation, increasing the operating temperature of the microprocessor structure, and potentially generating errors or causing physical deterioration and destruction if the heat is not adequately dissipated. This situation is exasperated by operating within a very confined cartridge volume. 
   To date, expansion cartridges have not used microprocessors so that there has been no need for, nor effort expended to create, a cartridge heat dissipation structure. The heat dissipation problem for add-on cartridges or integrated circuit assemblies is not limited to printers but also extends to other add-on products having microprocessors or other sophisticated components. In general, it is a common problem with add-on electronic devices that are installed in most electronic equipment. 
   In order to prevent malfunction of, or damage to, elements in the cartridge, the cartridge housing or casing is typically designed to maintain a maximum temperature of about 80° C. In order to maintain the surface temperature within tolerances, or below a preset value, it is important to devise a cartridge structure that makes it easy to dissipate heat from any microprocessor or other heat generating components within the cartridge to the surrounding environment. 
   To assist with thermal dissipation, this type of add-on device or cartridge employs a thermally conductive housing or case typically made from aluminum which allows conduction and radiation of heat to the surrounding environment. While a conductive housing effectively intercepts electromagnetic radiation, it can also re-radiate the deposited energy if it is not re-directed to a suitable ground or fixed voltage potential. This could generate noise in, or spurious interference with, sensitive components and circuitry positioned adjacent to the housing. Depending on the method of manufacture, such housings or cases also often provide through-paths along which electromagnetic radiation can “leak” when circuits are operating at certain desired frequencies. 
   What is needed is a new method and apparatus for dissipating heat generated in add-on circuits while reducing undesirable electromagnetic radiation and signal noise outside of the cartridge. 
   SUMMARY OF THE INVENTION 
   In order to solve the problems encountered in the art, one purpose of the present invention is to provide an add-in cartridge for electronic equipment which has improved electromagnetic radiation isolation. 
   An advantage of the cartridge is that any transfer of undesirable electromagnetic radiation to a surrounding environment from a built in microprocessor and other circuit elements is greatly reduced. 
   An additional purpose of the invention is to offer a cartridge for electronic devices which is capable of efficiently cooling internal circuit elements. 
   Another advantage of the invention is that a cost effective minimum complexity solution is provided for heat dissipation problems. 
   These and other purposes, objects, and advantages are realized in an add-on or add-in electronic circuit or cartridge which is configured for insertion into a predesigned connector or receptacle in an electronic device. The electronic device has an insertion opening or slot for receiving the cartridge, and at least a first processor for performing certain predefined logical operations within the electronic device. The cartridge is provided with conductive shielding positioned around or adjacent to at least certain noise producing portions, and at least one electrical conductor or conductive element which is connected between the shielding and at least one conductive element or surface, such as an interior support frame, within the electronic device. By providing the cartridge with conductive shielding, transfer of electromagnetic radiation based noise to a surrounding environment is effectively inhibited. Entire electronic systems can be developed using this type of cartridge structure to minimize the impact of extraneous electromagnetic radiation. 
   A first memory in the electronic device is connected to the first processor and used to store programs or processing steps for execution by the processor. An address signal line is also coupled between the processor and the add-on or add-in connector. An address output element or controller is connected in series with the address signal line and the add-on connector which converts print and command data into address signals which are transferred to the cartridge through the connector. Therefore, a read-only address line reflects data to be processed outside of the electronic device. 
   The cartridge employs a second, generally digital, processor which performs certain logical operations independent of those of the first processor and is preferably mounted on a circuit board. Conductors may also be used to electrically connect the shielding, fixed potential conductors on the circuit board, and the electronic device conductive element. This results in stabilization of any potential difference between the shielding, the circuit board, and the electronic device the cartridge is installed in, which prevents generation or transfer of electromagnetic noise resulting from currents between these elements. 
   A second memory is generally used in the cartridge to store programs or steps executed by the second processor and a data fetch device that fetches or decides data reflected in the address information transferred from the electronic device connector, or address line. 
   The add-in cartridge generally houses the circuit board in a case which incorporates the shielding and at least part of the case is metal with the remainder being provided with at least a layer or coating of conductive material. The case is generally manufactured using first and second mating case elements or shells. An overlapping ridge or shoulder is formed adjacent to the matting surfaces to preclude formation of a through-path for radiation. A layer of conductive material is formed on, and adjacent to, mating surfaces of at least one of the two case elements, to prevent noise producing electromagnetic radiation from escaping through the mating joint of the two case elements. This is particularly important for portions of the cartridge that may protrude from the electronic device when the cartridge is installed. In one embodiment, one of the two case elements is manufactured from a plastic material, and the other from a metallic material. 
   Connection elements should electrically connect conductors on the circuit board to the shielding at multiple locations to reduce any impedance between the two to effectively prevent the generation of high frequency noise. If the case is manufactured with a through-hole, such as for an electrical plug which interfaces with the electronic device, shielding connections should bridge at least one intermediate position within the through-hole. This position is typically located at a midpoint between ends of an elongated through-hole from which a connector plug protrudes. Since the wavelength of electromagnetic radiation that can be emitted from the through-hole is reduced by this configuration, harmful electromagnetic noise at the wavelengths of interest, such as that specified in government regulations, is effectively reduced. 
   The connection elements may also include one or more elastically deformable conductive elements electrically connected to the shielding, which have a portion that protrudes outside or the cartridge through an opening in the case. The protruding elements also electrically connect to a conductive element or surface within the electronic device when the cartridge is installed. Preferably, multiple elastic conductive elements are used to assure that at least one forms an adequate electrical connection with conductive surfaces in the electronic device. The multiple conductive elastic members may also electrically connect the shielding and fixed potential or power source conductors on the circuit board. 
   With respect to heat dissipation characteristics of the cartridge, metallic heat dissipation material is secured to the inside of the case and adjacent to a top surface of the second processor with an intervening thermal transfer element being disposed between and in contact with the two. This allows heat generated by the second processor to be dissipated to the outside through the heat dissipation material and the case. Furthermore, if an elastic biasing element is provided which pushes the second processor toward the heat dissipation material, the thermal resistance between the second processor, intervening member and heat dissipation member is reduced. 
   In further embodiments, an expansion memory connector is provided on the circuit board, along with an expansion access slot in the cartridge housing and a removable expansion slot cover. This configuration allows easy addition of memory as required for specific applications by simple insertion of expansion memory cards into the expansion memory connector. However, the expansion slot cover should be disposed in a position that is hidden inside the electronic device when the cartridge is inserted in the electronic device to prevent inadvertent removal or insertion of expansion memory while the cartridge is in use. Configuring the expansion memory as an IC card greatly simplifies memory expansion. 
   By also providing the cartridge with a joining device that mechanically joins the cartridge and the main electronic device, such as to the device housing, theft of the cartridge can also be prevented. The joining device may also employ a locking device which incorporates an electrical switch which can be connected to the power source for the cartridge. Therefore, in this embodiment locking the cartridge in place also activates the cartridge. 
   In further aspects of the invention the cartridge uses an address output means that reflects the data to be transferred to the outside in an address signal and outputs the address signal via the connector, a second memory that stores the procedures executed by the second processor, a data fetch device that fetches data reflected in the address from the address signal output from the electronic device, a circuit board on which are mounted the second processor, the second memory and the data fetch device. 
   Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings wherein like reference symbols refer to like parts. 
       FIG. 1  illustrates a perspective view of one embodiment of a cartridge structure constructed according to the principles of the present invention; 
       FIG. 2  illustrates an exploded perspective view of the cartridge of  FIG. 1 ; 
       FIG. 3  illustrates an enlarged perspective view of a printed circuit board used in the cartridge of  FIG. 1 ; 
       FIG. 4A  illustrates a plan view of a lower case of the cartridge of  FIG. 1 ; 
       FIG. 4B  illustrates an end view of a lower case of the cartridge of  FIG. 1 ; 
       FIG. 5  illustrates a plan view of the printed circuit board of  FIG. 3  without components installed; 
       FIG. 6A  illustrates a side view of the printed circuit board of  FIG. 3  positioned above the lower case of  FIG. 4 ; 
       FIG. 6B  illustrates a side view of the printed circuit board of  FIG. 3  mounted in the lower case of  FIG. 4 ; 
       FIG. 7  illustrates an enlarged cross-sectional view of the cartridge of  FIG. 1  showing principal parts positioned near a cartridge microprocessor; 
       FIG. 8  illustrates a perspective view of the cartridge of  FIG. 1  inserted in one type of printer; 
       FIG. 9  illustrates a perspective view of the cartridge of  FIG. 1  inserted in another type of printer; 
       FIG. 10  illustrates a longitudinal cross section of the cartridge of  FIG. 1  inserted in a printer frame of a first type; 
       FIG. 11  illustrates a longitudinal cross section of the cartridge of  FIG. 1  inserted in a printer frame of a second type; 
       FIG. 12A  graphically illustrates electromagnetic noise measurements taken before implementing noise countermeasures; 
       FIG. 12B  graphically illustrates electromagnetic noise measurements taken after implementing noise countermeasures; 
       FIG. 13  illustrates a cartridge joined to a printer using a chain; 
       FIG. 14  illustrates a cartridge having a keyed lock mechanism; 
       FIG. 15  illustrates a block diagram of the overall structure of a printer with a cartridge installed; 
       FIG. 16  illustrates a configuration for signal lines in a printer connector; 
       FIG. 17  illustrates an address map for a cartridge when viewed from the point of view of an electronic control device; 
       FIG. 18  illustrates an address map for a cartridge when viewed from the point of view of a cartridge microprocessor; 
       FIG. 19  illustrates a block diagram of a cartridge constructed according to the invention; 
       FIGS. 20A ,  20 B, and  20 C illustrate schematics of exemplary circuits useful for implementing interrupt request register  640  of  FIG. 19 ; 
       FIG. 21  illustrates a schematic of an exemplary circuit useful for implementing polling command register  643  of  FIG. 19 ; 
       FIG. 22  illustrates explanatory contents of status registers  645  of  FIG. 19 ; 
       FIG. 23  illustrates a schematic of an exemplary read control circuit  620  as used in  FIG. 19 ; 
       FIG. 24  illustrates a flowchart of processing steps used by control circuit  501  of  FIG. 19  for transferring data using read control circuit  620 ; 
       FIG. 25  illustrates an exemplary data structure inside of a storage ROM used in the cartridge of  FIG. 19 ; 
       FIG. 26  illustrates a flowchart of processing steps performed by the cartridge of  FIG. 19  for using a read control circuit  620  to transfer data; 
       FIG. 27  illustrates a flowchart of processing steps used by the electronic control device of  FIG. 9  to transfer data using a FIFO control circuit; 
       FIG. 28  illustrates a flowchart of processing steps performed by the cartridge of  FIG. 19  for transferring data using a FIFO control circuit; 
       FIG. 29  illustrates a schematic of an exemplary double-bank control circuit for use in the cartridge of  FIG. 19 ; 
       FIG. 30  illustrates a flowchart of processing steps used for starting the transfer of data with the double bank control circuit of  FIG. 29 ; 
       FIG. 31  illustrates a flowchart of response processing steps executed in the electronic control circuit of  FIG. 15 ; 
       FIG. 32  illustrates a flowchart of processing steps executed for transferring data using the double-bank control circuit of  FIG. 29 ; 
       FIG. 33  illustrates a flowchart of processing steps used for receiving data using the double bank control circuit of  FIG. 29 ; 
       FIG. 34  illustrates graphical representations of the timing relationships involved in printing image data by controlling the laser engine  505  with an electronic control circuit; and 
       FIG. 35  illustrates a cross section of major components of a cartridge using a compressible material to push directly on a microprocessor; 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Exemplary embodiments of the present invention are disclosed in relation to: the physical structure and components used; electromagnetic noise test results; alternative cartridge embodiments; overall printer and cartridge combination structure, and certain other aspects of applications of the invention. 
   The invention is disclosed and embodiments described along with related background and implementation material in relation to the following general outline. 
   I. Cartridge Structure 
   A. Physical Structure 
   B. Electromagnetic Noise Test Results 
   C. Alternative Cartridge Embodiments 
   II. Electrical Configuration of Printer and Cartridge 
   A. Overall Configuration 
   B. Cartridge Address Space 
   C. Internal Cartridge Structure 
   D. Data Transfer Controller 
   E. Registers 
   F. Read Control Circuit Configuration and Operation 
   G. FIFO Control Circuit Configuration and Operation 
   H. Double-Bank Control Circuit Structure and Operation 
   I. Image Data Printing 
   III. Miscellaneous aspects of the invention 
   Each section teaches certain aspects of the invention and its useful application to the laser printer art. In addition, the description is followed by an Appendix A which lists the numerals used in the figures along with corresponding element descriptions. 
   I. Cartridge Structure 
   A. Physical Structure 
   The present invention provides a method and apparatus for minimizing electrical noise or interference caused by the transfer of electromagnetic radiation from add-on data processing devices such as expansion cartridges for laser printers. The add-on device or cartridge uses a housing or casing designed to provide substantially complete electromagnetic shielding and eliminate direct transfer paths to the cartridge exterior for any radiation generated within the cartridge. 
   A perspective view of one embodiment of a printer-cartridge-type of add-on electronic device which is constructed and operating according to the present invention is illustrated in  FIG. 1 . An exploded perspective view of this cartridge is then illustrated in  FIG. 2 . The cartridge ( 503 ) illustrated in  FIG. 1  is designed for insertion into an expansion slot of the type commonly found on many laser printers for adding font capabilities. However, as discussed further below and in the co-pending patent applications listed above, the inventive cartridge is also able to receive print data from the printer, process and develop the received data into image data, and provide the results back to the printer for producing an output image. 
   In  FIG. 2 , a cartridge  503  is shown having a multi-layer printed circuit board  550 , called printed circuit board below, mounted inside of a generally upside-down U-shaped upper casing, shell, or housing  100  which has a recessed edge and a mating, plate-like, lower casing, shell, or housing  120 . A cap or end cover composed of a lower cap  140  and an upper cap  150 , is mounted on one side, or end, of the cartridge adjacent to a connector end of printed circuit board  550 . A heat generating circuit element, component, or device, such as a microprocessor  601 , is shown installed on printed circuit board  550 . The cartridge end where caps  140  and  150  are located is referred to as the front of the cartridge and the opposite end of the cartridge, where the microprocessor  601  is positioned, is referred to as the rear of the cartridge. 
   Upper case  100 , lower cap  140 , and upper cap  150  are typically made from a lightweight, easily manipulated material such as, but not limited to, ABS resin. Manufacturing the cartridge casings from non-metallic material provides a low cost advantage for providing a less expensive case, and making it lighter in weight and easier to transport or carry. Lower case  120  is typically manufactured from a lightweight metallic material such as aluminum. Aluminum is preferred because it has a high thermal conductance rate and is very effective at conducting heat to the outside of the cartridge. 
   A conductive layer is formed on the inside surface of upper case  100 , which together with lower case  120  constitutes a frame ground. An exemplary conductive or metallic material for the conductive layer on upper case  100  is electrodeless copper-nickel plating. In the alternative, the conductive layer can also be formed by using vacuum deposition of a conductive coating material, such as aluminum, or by applying a conductive paint or other liquid based coating material containing metal or conductive material. Alternatively, upper case  100  can be manufactured from a conductive plastic material which does not require a conductive coating. 
   An insertion plug  551  is formed on a top or bottom surface of the front end of printed circuit board  550 , and consists of a series of electrodes or contacts arranged in parallel on surfaces of the board for contacting matching electrical contacts inside the printer cartridge slot. The number of contacts is determined by the corresponding size of a matching connector conventionally provided in the printer. Plug section  551  may also employ orientation slots or guides, if also used in the printer. 
   In this embodiment, microprocessor  601  and other circuit elements are shown installed toward the rear of printed circuit board  550 , or the end opposite insertion plug  551 . Microprocessor  601  is typically secured in this location by soldering processor connection pins  601   p  to contact pads on printed circuit board  550  after insertion through contact/mounting holes or vias. However, it is contemplated that other mounting techniques may be employed such as surface mounting technology or, where space permits, a socket assembly could be provided. Four springs  104  are secured to outer edges of printed circuit board  550 . Two of the springs  104  are mounted near the center of the board and have spring leafs oriented substantially parallel to the direction of insertion for the cartridge. The other two springs are mounted at or near the rear of cartridge  503 . Springs  104  are used to electrically connect ground potential conductors, traces, or wiring on printed circuit board  550  and the conductive layer on the inside surface of upper case  100 . 
   Two grounding springs  122  are shown mounted toward the front of lower case  120  for obtaining grounding contact or a ground connection with a frame of the printer or other receiving electronic apparatus. Springs  122  are typically secured in place by fasteners such as rivets  123 . Springs  122  have a shape that approximates a bird with its wings spread. First curved extensions or components  122   a , which would correspond to right and left wings, each arch upward from the edges of a main spring body, while a second curved extension  122   b , corresponding to a bird&#39;s feet, extends downward from the main spring body in the shape of a semicircular arc. First curved extensions  122   a  act to electrically connect lower case  120  with ground or fixed potential conductors on printed circuit board  550 . Second curved extension or component  122   b  protrudes through generally rectangular openings  132  formed in lower case  120  and extends outside of cartridge  503 . At least one of the two, or more, spring extension  122   b  makes electrical contact with a conductive frame within the printer adjacent to the cartridge, and electrically connects lower case  120  with a grounding element of the printer to provide an adequate ground for cartridge  503 . 
   A wall-shaped mating member  124  is provided around the periphery of lower case  120  which extends upward from plate member  121 . Mating member  124  mates with the sides of upper case  100  by fitting inside of the walls of upper case  100  and completes the nearly rectangular case structure. 
   In order to exert an upward bias to, or bending force on, printed circuit board  550 , a resilient or compressible bias element  126  is placed on a bias retainer  128  on an inner surface at the rear of lower case  120 . Bias element or piece  126  is typically formed from a cylindrically shaped compressible, elastic, or resilient material such as silicon rubber and presses against printed circuit board  550  in an area directly beneath microprocessor  601  to push this area, and, thus, microprocessor  601  upward. However, those skilled in the art will recognize that other compressible or elastic materials may be used for this bias (pressure) function. 
   A sheet of heat dissipating material  102 , such as a piece of silicon rubber, is disposed between an upper surface of microprocessor  601  and an inner surface of upper case  100  to improve the closeness of fit or thermal contact between these elements and, therefore, the corresponding thermal conductance. Material having good thermal conductance is used for manufacturing heat dissipating material  102 . For example, Shin-etsu (trade name) silicon sheets manufactured by the Shin-etsu Polymer Company Limited, TC-CG type (trade name) silicon sheets manufactured by Shin-etsu Chemical Company Limited, and Sakon (trade name) manufactured by Fuji High Polymers may be useful materials. Each of these materials possess a relatively high thermal conductance rate of 1 W/m·K or more. Heat dissipating material  102  typically comprises silicon rubber but other materials may be used, as long as they effectively conduct heat. 
   Alternatively, materials that are initially in a non-solid state, such as viscous liquid, putty, or grease-like states, but harden when used, can also be used on the upper surface of microprocessor  601 . An exemplary material is the RTV (trade name) rubber compound from Shin-etsu Kagaku Kogyo K. K. If such a non-solid material is used, good surface contact between microprocessor  601  and upper casing  100  is obtained using a small quantity or thickness of material. Therefore, even a material with a relatively low thermal conductance rate provides adequate heat dissipation in&#39;this configuration. 
   A heat dissipation plate  110 , made from thermally conductive material such as aluminum, is also mounted on lower case  120  so that it covers the top of microprocessor  601 . As compressible bias element  126  pushes upward on printed circuit board  550 , microprocessor  601  is also pushed upward, increasing the surface contact pressure between microprocessor  601  and heat dissipating material  102 , and between heat dissipating material  102  and heat dissipation plate  110 . As a result, heat generated by microprocessor  601  is efficiently transferred to lower case  120  through heat dissipation plate  110  where it is dissipated to the surrounding environment. 
   During assembly, two springs  122  are first secured to lower case  120  and silicon rubber bias element  126  is mounted in retainer  128 . Various circuit elements are mounted on printed circuit board  550  and the four springs  104  are inserted in their respectively prescribed holes and secured in place, typically by soldering. Printed circuit board  550  is then mounted on lower case  120 , and the rear corners (microprocessor  601  side) are secured in place with screws. Heat dissipation plate  110  is also secured to the side of mating member  124  on lower case  120  using fasteners such as screws. Upper case  100  is then mated with lower case  120 , and lower cap  140  is inserted. At this time, two projections or mounting tabs  141  extending from the back of lower cap  140  have through-holes that are inserted under corresponding holes in upper case  100 . In this configuration, plug  551  extends through a narrow slot  142  formed in lower cap  140 . Upper case  100  is secured in place, typically at three locations toward the front end, using screws  160 . Finally, cartridge  503  is completed as shown in  FIG. 1  by fitting upper cap  150  on upper case  100 , which covers the screws  160  and an expansion memory slot  106 . 
   One button lock  154  is provided on each side of upper cap  150 . Springs  152  are disposed inside of the button locks and push button locks  154  toward an outer edge of the cartridge and upper cap  150 . In the outer most position or extension of the button locks, tabs on the button locks interact with or engage retention elements formed on upper case  100  and lock upper cover  150  in place. When button locks  154  are manually pressed inward, the tabs on the button locks are released from the retention elements, releasing cover  150 . 
   An IC card  200  is also shown in  FIG. 2  which is used as an expansion memory device and employs multiple dynamic RAM elements. IC card  200  can be installed in cartridge  503  as required or desired to perform various tasks. When inserting IC card  200 , upper cap  150  is first removed to gain access to an expansion card insertion slot  106  provided in upper case  100 . IC card  200  is inserted through slot  106  into an IC card connector  210  mounted on printed circuit board  550 . Whenever upper cap  150  is attached, cartridge  503  again appears as shown in  FIG. 1 . In this embodiment, an IC card is inserted by simply removing a small removable upper cap  150 . Therefore, use of an IC card does not require disassembly of the upper and lower cases, thus simplifying memory expansion. Further, by disposing upper cap  150  at the front of cartridge  503 , IC card  200  cannot be inserted or removed once cartridge  503  is inserted in main laser printer unit. This minimizes potential for damage and task interruption, caused by improper removal or insertion of the IC card. 
   An enlarged perspective view of printed circuit board  550  is shown in  FIG. 3 . In  FIG. 3 , microprocessor  601  is shown as being attached toward the rear of an upper surface of printed circuit board  550 , and insertion plug  551  is formed at other end. 
   A series of ROMs  606 ,  607 ,  608 , and  609 , are shown positioned near microprocessor  601  generally along the edges or sides of printed circuit board  550 . These ROMs are used to store one or more control programs, etc., for execution by microprocessor  601 . Four address buffers  617  are also shown mounted adjacent to microprocessor  601  in a square configuration in the center of printed circuit board  550 . Two clock oscillators  661  and  665  form the basic timing elements for microprocessor  601  and other components and are disposed along one edge. IC card connector  210  is positioned between tri-state buffers  617  and plug section  551 , offset slightly from board center. ASIC (application specific LSI) devices, which include control circuits, registers, etc., and ROM for storing processing programs for use by the printer (main printer ROM), and other circuit elements are mounted on the underside of printed circuit board  550 . For clarity in illustration, any wiring-or interconnect patterns present on the top and bottom surfaces of printed circuit board  550  have been omitted. For all of the circuit elements or components described above, the specific configurations, whether parallel, grouped, or irregular, are for purposes of illustration, and are not intended as a limitation inasmuch as other configurations are also contemplated within the teachings of the invention. 
   Due to its complexity and the interconnection density, microprocessor  601  is typically manufactured or packaged as a pin grid array (PGA) type of device. However, those skilled in the art will readily understand that other package types such as the SOJ, SOP, and QFP (Quad Flat Pack) styles can be employed as desired within the teachings of the invention. An exemplary microprocessor  601  is the Am29030, with a typical operating clock speed of 25 MHz, which is a RISC type microprocessor manufactured by Advanced Micro Devices (referred to as AMD). 
   As stated above, cartridge  503 , is configured to be inserted into a cartridge slot otherwise used for providing printer font information. Common font cartridges merely hold a ROM, or ROMs, in which font data is stored and then used to recreate the font “style” for given text. In contrast, cartridge  503 , contains control circuitry in the form of microprocessor  601 , ROMs  606  through  609 , ROM  618 , and some ASIC-type circuitry which provide programmed processing functions for print data. 
   The printer connector into which cartridge  503  is inserted is configured according to predefined font cartridge connection specifications. According to these specifications, the printer receptacle or connector is provided with read only lines, in the form of an address bus, for reading data from the cartridge into the printer, but no signal lines for transferring data from the printer to the cartridge. However, the cartridge used for this embodiment of the invention also provides the ability to receive print data from the printer, develop it into image data using microprocessor  601  and associated circuitry, and return the processed data to the printer. Therefore, it is necessary to transfer print data from the printer to the cartridge using the read only lines in the connector. As a result, special processing is required by the printer microprocessor. 
   When cartridge  503  is inserted into the font cartridge or expansion slot of the printer, the processor inside the printer reads identification data stored in ROM  618  during printer or software initialization, or when power is applied to the printer. At this point ROM  618  exerts control over printer data processing within the printer. In response to the identification data, the printer processor begins processing image data according to processing programs or algorithms stored in and provided by ROM  618 . That is, the printer processor executes special processing according to the programs stored in ROM  618 . This special processing consists of generating addresses or address values that essentially contain one byte of print data (in the form of a PDL program), placing this address on the address bus, and communicating or transferring this address to cartridge  503  through the connector and plug  551 . ASIC elements in the cartridge receive this address and extract the one byte of print data contained or encoded in the address by deciphering and storing it in RAM, as described later. One page of print data is then retrieved from RAM by microprocessor  601  and processed according to a desired PDL program and developed into image data. In this manner, developed image data are transferred from cartridge  503  to the printer and an image is printed by a xerography unit. 
   It is readily understood that it is better to use a processor that operates at speeds reasonably faster than the printer processor for microprocessor  601 . The higher speed allows microprocessor  601  to receive and process data and provide image data back to the printer in less time than the printer processor could process the same data. At the same time, the printer is not substantially delayed or having to wait for data. This allows image development processing that must usually be executed by the printer to take place using a higher-speed microprocessor  601  and in essence have the net or effective processing speed of the printer increased. The circuitry inside of cartridge  503 , and its operation, is also described in detail in the co-pending patent applications referenced above. 
   A plan view of lower case  120  is shown in  FIG. 4A  and a cross section in a plane parallel to line  4 B— 4 B is shown in  FIG. 4B . However, a cross section of upper case  100  is also included within the illustration of  FIG. 4B . As shown in  FIG. 4A , lower case  120  mainly consists of a plate  121  and wall-like mating element  124 . Mating element  124  forms a substantially continuous wall around lower case  120  except for the area around screw holes  125  at the front end of the cartridge. As shown in  FIG. 4B , mating member  124  mates with an inner surface of the sides of upper case  100  so as to form a case with a nearly rectangular cross section. As mentioned above, lower case  120  is generally made from aluminum or other conductive material and a conductive layer is formed on the inside surface of upper case  100 . Therefore, conductive layers on the outer surface of mating element  124  and inside surface of upper case  100  overlap each other, which effectively prevents electromagnetic radiation generated by internal cartridge circuit elements from escaping the interior cartridge volume. 
   A bottom view of printed circuit board  550  (surface opposite surface on which microprocessor  601  is mounted) is shown in  FIG. 5 . For purposes of clarity in illustration, no circuit elements are shown mounted in  FIG. 5 . Multiple ground (or other fixed) potential (GND) contact pads  560 ,  562 ,  564 , and  566  are formed around the outside edge of printed circuit board  550 . These pads are portions or areas of, or are connected to, a conductive layer provided for use as signal ground on printed circuit board  550 . 
   As can be seen from a comparison with  FIG. 2 , two ground pads  560  disposed near the rear of printed circuit board  550  (top of  FIG. 5 ) are formed in areas that include through-holes in circuit board  550  for screws used to secure the printed circuit board to lower case  120 . These pads are also formed with mounting holes, here three, for insertion of mounting prongs for springs  104 , which electrically connects each spring to the corresponding pad. Two ground pads  562  disposed near the middle of printed circuit board  550  are also formed in with additional mounting holes in circuit board  550 , again three, for mounting more springs  104 . Two ground pads  564  located near or along the front end of printed circuit board  550 , and a ground pad  566  located in the middle between pads  564 , are formed with through-holes for screws  160  used to secure printed circuit board  550  to lower case  120 . 
   When cartridge  503  is assembled, ground pads  560  and  562  are electrically connected to the conductive layer on the inside surface of upper case  100  through spring members  104 . At the same time, ground pads  560 ,  564 , and  566  are electrically connected to lower case  120  by contact screws extending through screw holes in lower case  120 . As a result, the ground conductor (signal ground or SG below) of printed circuit board  550  is connected to the conductive layer (frame ground or FG below) of the case at multiple locations. By connecting SG and FG at multiple locations, the impedance between SG and FG can be reduced and the generation of high frequency eddy or parasitic currents prevented. This in turn prevents generation of extraneous electromagnetic radiation (electrical noise). 
   As shown in  FIG. 2 , since the conductive layer does not extend around through-hole  142  in lower cap  140 , electromagnetic radiation can escape or exit from the cartridge in this region. As is well known in the art, there are various national or international standards established for acceptable levels of electromagnetic radiation and noise or interference. These standards are enforced by governmental departments or agencies such as the Federal Communications Commission (FCC) in the United States, VCCI in Japan, etc. The regulations used by these agencies typically prescribes a frequency range of between 30 to 1,000 MHz as delimiting undesirable noise signals. Therefore, if electromagnetic radiation in this frequency range can be reduced, harmful noise or interference, as defined, can be prevented. From this standpoint, ground pad  566  near the middle of plug  551  ( FIG. 5 ) is provided to reduce undesirable noise by decreasing the wavelength of the electromagnetic radiation emitted from through-hole  142 . In this embodiment, the wavelength is decreased by approximately a factor of two (i.e., approximately doubling the frequency). 
   A side view of circuit board  550  is shown in  FIGS. 6A and 6B  for use in detailing the electrical connection of printed circuit board  550  and lower case  120  using springs  122 . Printed circuit board  550  is shown in  FIGS. 6A and 6B  as before and after being placed on lower case  120 , respectively. As shown in  FIG. 6A , there is a gap between first curved member  122   a  of spring  122  and mating member  124  of lower case  120 . In  FIG. 6B , first curved member  122   a  presses against printed circuit board  550 , but there is still a small gap between mating member  124  and curved member  122   a . Since the end of curved member  122   a  is divided into three parts, each of which functions separately as a spring member, spring  122  and the ground conductor on the bottom surface of printed circuit board  550  are reliably electrically connected. Springs  122  also act to prevent generation of electromagnetic noise. 
   First curved spring members  122   a  may be connected to conductors having potentials other than ground. That is, they may also be used to electrically connect power source wiring supplying regulated voltage (such as 3 V, 5 V, etc.) for driving microprocessor  601  and other peripheral circuits, to lower case  120 . These elements may also be connected to power source wiring for regulated or stabilized voltages provided by separate power source wiring. 
   An enlarged cross section of the mounting area for microprocessor  601  on circuit board  550  of  FIG. 5  is shown in  FIG. 7 . In  FIG. 7 , compressible material  126  is shown positioned in a retaining section  128  of lower case  120 . A heat dissipating material  102  is mounted between the upper surface of microprocessor  601  and heat dissipation plate  110 . The compressible material presses or biases printed circuit board  550  upward under microprocessor  601  which is shown attached on top of printed circuit board  550 . This creates good thermal contact between microprocessor  601 , heat dissipation material  102 , and heat dissipation plate  110 , and improves heat dissipation across these elements. Heat generated by microprocessor  601  is discharged through material  102 , heat dissipation plate  110 , and lower case  120 , where it is discharged to the surrounding air. 
   In addition, as shown in  FIG. 7 , a number of passages or holes are formed in end surface  108  of upper case  100  to make a surface structure through which air easily passes. Therefore, these holes are also effective in dissipating heat from inside of cartridge  503  to the outside. Using or forming several air passages in edge surface  108  effectively increases the surface area, which also improves heat dissipation. However, when other heat dissipation measures are deemed adequate, it is not necessary to provide openings in edge surface  108 . Further, it is better not to open holes in end surface  108  when trying to reduce electromagnetic noise. 
   Perspective views of cartridge  503  after insertion into a first type of printer  1 A and a second type of printer  1 B are illustrated in  FIGS. 8 and 9 , respectively. Longitudinal cross sections of inserted cartridge  503  in relation to frames  180  and  182  of printers  1 A and  1 B, are then shown in  FIGS. 10 and 11 , respectively. However, in  FIGS. 10 and 11 , the circuit elements, etc., and the cross hatching normally used to illustrate a cross section, are omitted for purposes of clarity in illustration. 
   As shown in  FIG. 10 , plug  551  of printed circuit board  550  has been inserted into an interface connector CN 11  for printer  1 A. In this position, at least one spring component  122  at the rear, or non-connector end, of cartridge  503  makes electrical, and thermal, contact with metal frame  180  of printer  1 A. As shown in  FIG. 11 , at least one spring component  122  at the front, or connector end, of cartridge  503  makes electrical, and thermal, contact with metal frame  182  of printer  1 B. This means that one of the two spring members  122  comes into contact with a grounded portion of the main printer unit and the cartridge case and the printer are reliably electrically connected. 
   Therefore, as described above, several anti-noise countermeasures are implemented for inhibiting the generation of electromagnetic noise or interference from or by the cartridge. These measures can be summarized as: 
   (1) Forming a conductive layer on inside surfaces of plastic upper case  100 , while manufacturing the lower case from a metal such as aluminum so that a conductive layer or barrier is formed over the entire interior of the cartridge case to effectively block transmission of electromagnetic radiation to the outside of the cartridge. 
   (2) A wall-like mating member  124  is provided around the periphery of lower case  120  which fits inside of upper case  100 . This results in conductive layers on the outer surface of mating member  124  and inside surface of upper case  100  overlapping to effectively block transmission of electromagnetic radiation to the exterior of the cartridge. 
   (3) Signal and frame grounds are connected at multiple locations to decrease any impedance between them, and to suppress the generation of high frequency eddy or stray currents. 
   (4) Signal and frame grounds are connected both on the sides and middle of plug  551  near through-hole  142 , to reduce the wavelength of electromagnetic radiation that can be emitted from through-hole  142  (frequency is increased). This reduces electromagnetic noise in the wavelength band of interest that is typically the subject of regulations relating to electrical noise or interference. 
   These countermeasures are also followed by implementing two more general countermeasures in cartridge  503 . 
   (5) A decoupling capacitor is provided near the ground terminal or pin of each of the circuit elements and the power source terminal. 
   (6) A common mode choke coil is provided in series with the power source conductor for microprocessor  601 . 
   B. Electromagnetic Noise Test Results 
   A graph representing measurements of electromagnetic noise for the cartridge taken before electromagnetic noise countermeasures were implemented is shown in  FIG. 12A . Another graph of these measurements taken after implementing an embodiment of the invention is shown in  FIG. 12B . In  FIGS. 12A and 12B , the single-dot dashed line indicates an FCC guideline or acceptable electromagnetic noise standard. The countermeasures, designated as items ( 2 ) through ( 6 ) above, were not implemented in the cartridge before the first countermeasure was taken, and both upper case  100  and lower case  120  were made from aluminum. As can be seen from  FIGS. 12A and 12B , the above countermeasures reduce measured electromagnetic noise considerably, and after such countermeasures are taken the cartridge sufficiently satisfies typical governmental regulations, such as those promulgated by the FCC. 
   C. Alternate Cartridge Embodiments 
   To prevent theft of the cartridge, the cartridge and main printer unit can be mechanically connected.  FIG. 13  shows cartridge  503  and printer  1  connected by a chain  570 . A hole or reinforced passage  572  is formed in the end of cartridge  503  that remains to the exterior of the printer, and a ring  573  is passed or inserted through hole  572  and secured in place. One end of chain  570  is attached to the ring, and the other end is secured with a screw or similar fastener to printer  1 . Here the chain is illustrated as being secured to a ground terminal  574  of the printer for convenience, and to prevent the chain from acting as a radiating element for electromagnetic radiation. 
   In the alternative, a lock mechanism can be employed as illustrated in  FIG. 14 . In  FIG. 14 , a cartridge  503  is shown using a keyed lock mechanism  580 . When a key is inserted in mechanism  580  and turned, a protruding element  582  contained inside cartridge  503  is extended inside of printer  1  and engages a groove or depression (not shown) at a corresponding position in the printer. The lock pin could also be extended to engage any portion of the frame surrounding the slot in which cartridge  503  is inserted. Using this approach, cartridge  503  is prevented from being removed from the printer. Those skilled in the art will appreciate that key lock mechanism  580  can also be configured to provide an electrical switching function so that turning the key not only locks cartridge  503 , but also switches or engages a power source for the cartridge. Instead of a chain- or lock mechanism, cartridge  503  can also be secured to the printer with a screw to prevent theft. 
   While an IC card was used as an expansion memory device in the above embodiment, SIMMs (single in-line memory module) or other types of portable expansion memory elements can also be employed as desired within the teachings of the present invention. 
   H. The Electrical Configuration of the Printer and Cartridge 
   A. Overall Configuration 
   A general block diagram of a laser printer  500 , in which cartridge  503  is used is illustrated in  FIG. 15 . In  FIG. 15 , laser printer  500  is shown being equipped with an electronic control device, unit, or circuit  501 , which controls all of the operations of laser printer  500 , and a laser engine  505  which forms an output image on paper or other transfer media P. Laser printer  500  is shown as being connected to a computer or work station  507  as a source of print data. Electronic control circuit  501  generates or develops image data, in the form of bit-mapped data, from the print data provided by, or transferred from, work station  507 . The image or developed image data is transferred from controller  501  to laser engine  505  through a connector CN 10  where a xerography unit  15  responds to the data and forms an output image on paper P. 
   As shown in  FIG. 15 , electronic control circuit  501  is equipped with a commonly known microprocessor or central processing unit (CPU)  510 , here chosen to be a MC68000 processor which is manufactured by Motorola. Control circuit  501  also employs a ROM  511  for storing programs for execution by the printer CPU; a RAM  512  for storing post developed print and image data; a data input/output port  514  for receiving print data from work station  507 ; a line buffer  515  attached to a bus line  516  for transferring data exchanged with cartridge  503 ; a register  517  for exchanging command and status data with laser engine  505 ; a console panel interface I/F  519  for providing interface control between laser printer  500  and a console panel  518 ; and a double buffer circuit  520  for retaining image data sent to laser engine  505 . 
   As seen in  FIG. 15 , an exemplary double buffer circuit  520  makes use of two RAMs, RAM  520 A and RAM  520 B, which each typically accommodate up to eight lines of print data for laser engine  505 , which corresponds to 4 kilobytes of memory capacity. A memory write controller  520 C is used to alternately write image data to one of these RAMs from CPU  510 . A memory read controller  520 D alternately reads data from each of the two RAMs,  520 A and  520 B, and transfers that data to laser engine  505  where it is converted into video signals synchronized with the timing of the rotation of the photosensitive drum in order to print data. Two RAMs  520 A and  520 B are provided, and reading and writing of data takes place alternately, because CPU  510  and laser engine  505  are configured to access memory, these RAMs, independently. 
   After CPU  510  writes data to one of the RAMs, it sets a flag in a specific bit position of register  517  to show the presence of new data. Laser engine  505  then checks this flag and responds by reading image data stored in the RAM from the appropriate addresses to which it was written. During the reading process, another bit in register  517  is set to inform CPU  510  which RAM is being read to prevent access before the reading operation is terminated. Since only one RAM is being accessed by laser engine  505  at this time, CPU  510  writes the next eight lines of image data to the other RAM during this period. After the process of reading data from one RAM is complete, laser engine  505  resets the appropriate flag bit and proceeds to read data from the other RAM. The speed at which CPU  510  writes data is faster than the speed at which laser engine  505  reads data, that is, the print execution speed. Therefore, a memory access conflict between the two is generally automatically avoided and the transfer of one page of image data takes place simply and efficiently. 
   As stated, cartridge  503  is connected to control circuit  501  through connector CN 11 . A line buffer  515 , which has a bus driver (not illustrated) mounted somewhere along data bus  516 , acts as a one-way buffer that transfers data from connector CN 11  to CPU  510 . In other words, when viewed from the processing perspective of CPU  510 , cartridge  503  is a read only device. 
   When power is turned on or applied to printer  500 , electronic control unit or circuit  501  determines if a cartridge  503  is connected to connector CN 11 . If a cartridge is detected, an internal reset for control circuit  501  is activated. After being reset or performing initialization etc., control circuit  501  executes a jump to a pre-specified address of a ROM provided in cartridge  503  (discussed later). Subsequent to this jump, control circuit  501  sequentially executes processing steps provided by cartridge  503 . Meanwhile, cartridge  503  interprets the PDL data output to laser printer  500  from work station  507 , develops it into image data, and provides program steps to control circuit  501  so that the appropriate printing occurs using laser engine  505 . 
   The wiring relationship of plug  551 , formed on one end of printed circuit board  550 , and connector CN 11  is shown in  FIG. 16 . As shown in  FIG. 16 , plug  551  employs 25 pins on either side (sides A and B) of two sided printed circuit board  550 . In  FIG. 16 , a signal name is used to label each corresponding pin of plug  551 . A slash mark [/] affixed to a signal name indicates that the signal is active low [logical 0]. 
   In  FIG. 16 , /ASB represents an address strobe signal (ASB) transmitted by CPU  510  within the printer (here a Motorola MC68000), while /UDS and /LDS represent upper and lower data strobe signals output by CPU  510 . An auxiliary address strobe (ADS) or /ADS signal is an assist signal generated as a result of certain parameters and the status of address strobe signal /ASB in electronic control circuit  501 . The /ADS signal provides an indication of activity when the printer starts up or is initialized, which is different for different printers. As discussed later, in this embodiment, the printer type is determined according to activity or operation that takes place when the /ADS signal is initialized. 
   An output data acknowledge signal or /ODTACK signal is shown which is transferred from cartridge  503  to control circuit  501 . A cartridge select or /CTRGSEL signal represents a signal used by CPU  510  to select cartridge  503  and access ROM, registers, etc., that are allocated to internal address spaces. Addresses or address signals A 1  through A 20 , and read and write signal R/W, are both output by CPU  510 , while signals D 0  through D 15  are provided by cartridge  503 . A clock or SCLK signal is output by an oscillator (not illustrated) built into laser printer  500 . 
   A cartridge registration or detection or /CTRGS signal is provided in laser printer  500  which is pulled down or low when cartridge  503  is inserted. As a result, CPU  510  detects the presence of cartridge  503  when inserted into connector CN 11 . 
   CPU  510  typically uses 23-bit address signals for signals A 1  through A 23  to specify an address word and the /UDS and /LDS signals to specify high (upper) and low (lower) end bytes, respectively, of each word. As a result, CPU  510  is able to handle 16 megabytes of address space, generally residing at address values ranging from 000000h to FFFFFFh. Here the symbol ‘h’ that is attached to the end of the address indicates a hexadecimal number or unit. 
   B. Cartridge Address Space 
   Cartridge  503  is allocated some of the address space, specific address range, accommodated by CPU  510  in control circuit  501 . CPU  510  uses addresses within a range or space bounded by the values 000000h and FFFFFFh, for a 16-megabyte address space, but part of this address range is already allocated for use by ROM. The space allocated to cartridge  503  changes depending on the specific model or type of the laser printer. In the case of Hewlett-Packard laser printers, a 2-megabyte memory capacity or address space allocation for address values ranging from say 200000h to 3FFFFFh or from 400000h to 5FFFFFh is assigned, as shown on the left side of  FIG. 17 . 
   However, as previously discussed, the typical microprocessor  601  used in cartridge  503  is an AMD model AMD29030–25 MHz which can handle 4 gigabytes of memory at address values ranging from 00000000h to FFFFFFFFh. In addition to ROM and RAM allocations within this address space, allocation occurs for various registers used for data exchange with electronic control circuit  501 . This type of allocation is illustrated in  FIG. 18 . The configuration of components inside of cartridge  503  is described below along with address space requirements for both microprocessors used within the combined cartridge and printer system. 
   C. Internal Cartridge Configuration 
   The internal configuration of cartridge  503  is shown in  FIG. 19 . In  FIG. 19 , cartridge  503  is configured with a centrally located microprocessor  601  for controlling all cartridge operations. The cartridge is also shown using a memory section  602  with ROM, RAM, and support circuitry, a data transfer controller  603  to control data exchange with control circuit  501 , and some additional circuitry. 
   Memory section  602  employs a series of ROMs  606  through  609 , which generally aggregate to a total memory capacity of 2 megabytes, and are used to store programs for microprocessor  601  execution. A selector  610  is used to provide bank switching of ROMs  606  through  609 . RAMs  611  through  614 , also provide a total memory capacity of at least 2 megabytes, and are used to retain print data received from control circuit  501  and to also retain post developed image data. ROMs  606  through  609  are generally configured as mask ROMs, each having 16 bits by 256 kilobits of capacity, for a total of 4 megabits of memory. As shown in  FIG. 18 , ROMs  606  to  609  are allocated to address spaces 00000000h to 1FFFFFh. Each ROM set  606 ,  607 , and  608 ,  609  forms a 2-unit bank creating a 32-bit data bus. ROMs  606  and  609  and microprocessor  601  are connected by address bus AAB and a control signal bus. Data bus IDB of each of ROMs  606  to  609  is also connected to data bus DB 29  through data selector  610 . Therefore, microprocessor  601  is able to read data from ROMs  606  through  609 . All address signals, except the three low end bits (A 0 , A 1 , and A 2 ) from microprocessor  601  on address bus AAB, are input to ROMs  606  and  607 , and ROMs  608  and  609 . 
   The two low end bits (AO and Al) are not input because data is read by microprocessor  601  in units of one word, or thirty-two bits (4 byte units). In addition, if the third lowest address bit A 2  is not used when reading data, ROMs  606  to  609  output data simultaneously, and data selector  610  makes adjustments to data being output from the ROMs simultaneously. That is, the access of the ROMs by microprocessor  601  often takes place from consecutive addresses. Therefore, using 32-bit data words, consecutive words are read from ROMs  606  through  0 . 609 . If consecutive words are actually read, the two-set ROM banks are switched in sequence by data selector  610  and the data is read consecutively. As a result, reading two consecutive words or contiguous data is extremely fast. 
   RAMs  611  through  614  are each generally implemented as 16 by 256 kilobit DRAMs, for a capacity of 4 megabits. As shown in  FIG. 18 , these RAMs are allocated to 2 megabytes of address space or addresses from 20000000h to 201FFFFFh. An additional 2 megabytes of memory can be added to cartridge  503  using expansion RAM interface  615  which is allocated to addresses from 20200000h to 203FFFFFh. Typically, a maximum of 2 megabytes of SIMM type RAM can be installed in expansion RAM interface  615 . RAMs  611  through  614  and expansion RAM  615  data lines are connected directly to a data bus DB 29 , which is the microprocessor  601  data bus. The RAM address lines are connected to microprocessor  601  address bus AAB through a data transfer controller  603 . Register I/O, discussed later, is allocated to address spaces starting from 80000000h. 
   Returning to  FIG. 17 , when viewed from the perspective of control circuit  501 , cartridge  503  ROM is allocated to the first 128 kilobytes. That is, cartridge  503  contains programs that are to be executed by CPU  510 . When cartridge  503  is inserted or otherwise installed, CPU  510  executes a jump instruction to the address specified for this ROM after initialization is completed, and CPU  510  subsequently operates according to processing steps stored in this ROM. 
   When CPU  510  accesses the first 128 kilobytes of the 2 megabyte space allocated to cartridge  503 , ROM  618  is accessed using an address signal output through address buffer  617  provided for connector side address bus CAB of cartridge  503 . The commands and data stored in ROM  618  are sent to CPU  510  through data buffer  619  formed on data bus CDB of the connector. The ‘X’ used in labeling the FIFO (lower right) addresses in  FIG. 17  represents the four high end bits of the first address of the allocated address spaces. 
   D. Data Transfer Controller 
   A variety of control and status registers are accessed at addresses other than those addresses allocated to ROMs and RAMs in the address maps shown in  FIGS. 17 and 18 , and are provided for data transfer controller  603 , which is described next. The controller description chiefly relates to circuitry with further reference to address maps ( FIGS. 17 and 18 ) as appropriate. 
   Data transfer controller  603 , shown in  FIG. 19 , is formed using an ASIC having around 7,900 usable gates. An exemplary. ASIC found useful in manufacturing the invention is manufactured by Seiko Epson, and is a standard cell device, model number SSC  3630 , which exhibits low power consumption and is manufactured using a CMOS process. Data transfer controller  603  controls the exchange of data between control circuit  501  and microprocessor  601  of cartridge  503 . This data exchange uses a read control circuit  620  to send data through a read only data bus from control circuit  501  to cartridge  503 ; a FIFO control circuit  623  to pass data through a FIFO memory  621 , using read control circuit  620 ; and a double bank control circuit  624 , which makes it possible for control circuit  501  to read data from cartridge  503 . FIFO memory  621  is configured as a RAM-type memory device that sequentially stores and reads data using a first-in-first-out procedure. An exemplary component useful for implementing this RAM is a RAM circuit, part number M66252FP, manufactured by Mitsubishi Electric. 
   Address bus CAB is connected to data transfer controller  603  through address buffer  617 , and data bus CDB is connected through data buffer  619 . A first decoder  631 , formed in controller  603 , receives address bus CAB and cartridge selector CSEL signals and outputs selection signals to other elements in data transfer controller  603 . In a similar manner, address bus AAB and control signal CCC, from microprocessor  601 , are connected to transfer controller  603  using a bus controller  635  formed in controller  603 . A second decoder  632  is connected to address bus AAB and outputs selection signals to other data transfer controller  603  circuitry. Furthermore, bus controller  635  outputs address signals and control signals to ROMs  606  through  609  and RAMs  611  through  614 , as well as expansion RAM interface  615 . 
   In addition to the above elements, a variety of other registers are provided within data transfer controller  603 . Beside normal read and write operations, many other registers are automatically written to when special processing takes place. The configuration of these special registers is described below. 
   Taken from the control circuit  501  point of view, cartridge  503  is a read only device, and registers writable from control circuit  501  are configured to be written to using a read operation from a specified address. That is, by specifying a particular address, a selection signal is output from a first decoder  631  and data is written to a certain register as a result. Reading from the registers takes place using normal read cycle operations. Data reading and writing by microprocessor  601  also occurs using normal read and write operations. In  FIG. 19 , registers are shown as being connected to a readable bus, and write operations are simply indicated by arrows. Such registers include, interrupt request register  640 , polling command register  643 , status register  645  ( FIG. 17  register STATUS), transfer flag register  647  ( FIG. 18  register BPOLL), PROM control register  649 , and control register  650 . 
   Among these registers, registers other than status register  645  and transfer flag register  647  represent a generic name for multiple registers allocated as memory mapped I/O for CPU  510  or microprocessor  601  and are not necessarily allocated to consecutive addresses. Registers AMDINT 0 , AMDINT 1 , and AMDINT 2 , and registers AMDCLR 0 , AMDCLR 1 , and AMDCLR 2 , shown in  FIGS. 17 and 18 , belong to interrupt register  640 . Registers POLL and MCONTCS belong to polling command register  643 . The PROM control registers include the registers EEPCS, EEPSK, and EEPDI. 
   All registers not belonging to read control circuit  620 , FIFO control circuit  623  or double bank control register  624 , and not mentioned in the above description, generally belong to or form part of control register  650 . These are registers ADDMUXA, ADDMUXB, CLKDIV, RTCVAL, RTCON, RTCSEL, RTCCLR and SYSKEEP, which are shown in  FIGS. 17 and 18 . 
   Among the various portions of  FIGS. 17 and 18 , EWWRL and EWWRH, which are each 512 bytes in size, are memory areas used for writing to a first latch  651  and a second latch  652  of read control circuit  620  from control circuit  501 . Register EWRD is equivalent to seeing latches  651  and  652  as a one word latch from the microprocessor  601  point of view. Registers FIFOREQ, FIFORST, and FOFOW are equivalent to FIFO register  653  of FIFO control circuit  623 . Registers FIRCLK, RDCLK, FIFORD, and RDRST are equivalent to FIFO read register  655  of FIFO control circuit  623 . A latch  657  is also provided in FIFO control circuit  623  to maintain data to be written to FIFO memory  621  using some of the functions of read control circuit  620 . 
   Portions of  FIG. 17  labeled by the symbols DPRAMA and DPRAMB represent buffers having a 32 byte capacity. These buffers are equivalent to viewing first and second buffers  658  and  659  of double bank control circuit  624  from the control circuit  501  side. These banks, DPVVROA and DPWROB, shown in  FIG. 21 , are what is seen by microprocessor  601  when viewing buffers  658  and  659 . Certain bits d 1  and d 2  of status register  645  are also used for the exchange of data through double bank control circuit  624 . Details of this exchange are provided below. 
   E. Registers 
   Interrupt request register  604  is a register that generates, or transfers and retains an interrupt request from control circuit  501  to microprocessor  601 . Three levels, and three corresponding registers (AMDINT 0 , AMDINT 1 , and AMDINT 2 ), are provided for interrupt requests directed from control circuit  501  to microprocessor  601 , as shown in  FIG. 17 . An interrupt request to microprocessor  601  is generated by control circuit  501  reading any of the individual registers forming interrupt request register  640  which sets these registers. However, data read during this operation has no meaning and is generally irrelevant to the generation of interrupt requests. 
   A more detailed example of configurations useful for implementing interrupt request register  640  is illustrated in  FIGS. 20A ,  20 B, and  20 C in which registers are formed using D-type flip-flops. An output pin, Q, for each D-type flip-flop,  640   a ,  640   b , and  640   c , is set active low using the AMDINT 0 , AMDINT 1 , and AMDINT 2  signals, respectively, which are output by first decoder  631  during the register read operation described above. As before, the use of a “/” or slash symbol in front of a signal label indicates that the signal is active low. 
   As shown in  FIG. 18 , the corresponding registers that clear the respective outputs of flip-flops  640   a ,  640   b , and  640   c , are allocated to specific addresses as three read only registers AMDCLR 0 , AMDCLR 1 , and AMDCLR 2 , respectively. As a result, when a microprocessor  601  read operation from all of the addresses allocated to this register ( 640 ) takes place, a second decoder  632  outputs /INTCLR 0 , /INTCLR 1 , and /INTCLR 2  signals and the corresponding flip-flops are preset. 
   When an interrupt originates from control circuit  501 , one register in interrupt request register  640  must be accessed. Microprocessor  601  determines a priority and performs operations that apply to the interrupt request. In this case, microprocessor  601  clears the corresponding interrupt request registers  640   a ,  640   b , and  640   c.    
   Polling command register  643  is used to pass commands or instructions from microprocessor  601  to control circuit  501 , and it can be written to by microprocessor  601  and read by control circuit  501 . An exemplary hardware configuration for register  643  is shown in  FIG. 21 . As indicated in  FIG. 21 , command register  643  uses two octal D-type flip-flops,  643   a  and  643   b , which form a 16-bit wide data latch, and one D-type flip-flop,  643   c . A 16-bit wide data bus DB 29  originating from microprocessor  601  is connected to data input terminals or pins ID through  8 D of flip-flops  643   a  and  643   b , while a 16-bit data bus DB 68  originating from control circuit  501  is connected to output terminals,  1 Q through  8 Q. 
   Second decoder  632  outputs a /MCONTCS signal when microprocessor  601  accesses polling command register  643  ( FIG. 18 , register MCONTCS), which is input to clock terminals CK of flip-flops  643   a  and  643   b . When the leading edge of this signal goes low, the contents of data bus DB 29  are latched to flip-flops  643   a  and  643   b . In addition, first decoder  631  outputs a /POLL signal when control circuit  501  accesses polling command register  643  ( FIG. 17 , register POLL), which is connected to output-enable terminals OE, which enables the outputs of flip-flops  643   a  and  643   b . When this signal goes low, data retained in flip-flops  643   a  and  643   b  is output to data bus DB 68 . 
   The /MCONTCS and /POLL signals are connected to a clock pin C and preset terminal PR of D-type flip-flop  643   c . Flip-flop  643   c  generates a CMDRD signal on its output pin Q which is set high (logic 1) when DB 29  data is latched in flip-flops  643   a  and  643   b  (/MCONTCS is low) and reset low (logic 0) when this data is read by control circuit  501  (/POLL is low). A read enabled status register  645  connected to control circuit  501  uses a specific bit d 3  (also called flag CMDRD below) to determine the status of the CMDRD signal. Therefore, by reading status register  645 , control circuit  501  is able to know, or is provided with an indication from microprocessor  601 , that command code has been set in polling command register  643 . 
   When control circuit  501  observes the CMDRD flag, bit d 3  of status register  645 , and finds that an instruction or command has been placed in register  643 , it reads the contents of command register  643  during a normal read cycle. That is, it reads the command sent from microprocessor  601 . The commands are, for instance, to start transferring print data to data transfer controller  603 , to start printing, or to display messages on console  518 . As shown in  FIG. 21 , when control circuit  501  reads the contents of polling register  643 , CMDRD, output by flip-flop  643   c , its output is then reset high using the /POLL signal. Therefore, by observing a bit d 2  of transfer flag register  647 , microprocessor  601  is able to know whether or not the command it output Was read or received by control circuit  501 . 
   In addition to the data described above, which shows whether or not a command has been placed in the register by microprocessor  601 , status register  645  also retains the data illustrated in  FIG. 22 , which is described as follows. Bit d 0  of this data is set low by the EWRDY signal, which is generated within read control circuit  620  when data is written there by control circuit  501 , discussed later. When that data is read by microprocessor  601 , bit d 0  is set high by a signal from a second decoder  632 . This bit is generally referred to as the EWRDY flag or flag EWRDY. 
   Data bits d 1  and d 2  indicate whether or not double bank control circuit  624  has its access enabled either by control circuit  501  or microprocessor  601 . The respective flags are referred to as ADDMUXA and ADDMUXB. These two bits correspond to the two transfer banks built into double bank control circuit  624 . As shown in  FIG. 18 , bits d 1  and d 2  are set and reset by microprocessor  601  when writing data to bit d 0  of registers ADDMUXA and ADDMUXB, which are contained in control circuit  650 . Therefore, before writing data to one of the banks of double bank control circuit  624 , microprocessor  601  sets the flag to a low level and then resets it high after writing is finished. Assuming control circuit  501  reads data from the bank side in which this flag is set high (1), by alternately writing and reading the data to the two banks, microprocessor  601  connects to the control circuit  501  side and passes data. The function of the d 3  bit (flag CMDRD) has already been described above. 
   Bit d 5  acts as a flag CLKDIV, which is set according to the operation of the microprocessor  601  clock. Clock CLK, which is output from first oscillator  661  and typically employs an external liquid crystal vibrator CRC 1 , is used as the operating frequency for microprocessor  601 . If a value of zero is written to bit d 0  of a register CLKDIV of control register  650  from microprocessor  601 , the microprocessor clock is set to operate at a predetermined frequency, here 25 MHz. However, if a one is written to bit d 0 , the clock is set to operate at one-half of this frequency, or 12.5 MHz in this example. Flag CLKDIV of status register  645 , when observed from the point of view of control circuit  501 , is set low when clock CLK is operating at a its normal frequency, of 25 MHz, and set high (1) when this is decreased, to 12.5 MHz. Control circuit  501  checks bit d 5  in status register  645  to determine the clock frequency, that is, to know the current operating speed of microprocessor  601  in order to match the timing for data transfers, etc. 
   The d 6  bit acts as a flag referred to as ADMON, which is set high when microprocessor  601  is processing data and set low when microprocessor  601  terminates data processing and enters a sleep mode. In the preferred embodiments, microprocessor  601  receives PDL-type data from control circuit  501  and then performs the processing necessary to develop this data into image data. However, if no PDL-type data is provided by control circuit  501 , microprocessor  601  does not perform any data processing and is considered inactive. If this inactivity continues for a predetermined amount of time, microprocessor  601 , through oscillator  661 , is switched to a lower operating frequency to conserve power and decrease the amount of heat output. While those skilled in the art will recognize that several intermediate frequencies could be used, a preferred operating frequency for the initial sleep mode is one half of the initial operating frequency, that is, 12.5 megahertz in this example. If the inactivity extends for a significant period of time, microprocessor  601  ceases operation and enters a second sleep mode wherein the output of oscillator  663  is set to zero and microprocessor  601  is effectively turned off. When transitioning from the first to the second sleep state, or half frequency operation to off, microprocessor  601  writes a zero in register ADMON of control register  650 . As a result, bit d 6  of status register  645  is set low, and control circuit  501  can easily detect the current operating mode of microprocessor  601  by checking this bit. 
   A real time clock built into data transfer controller  603  is used to measure the amount of activity or inactivity of microprocessor  601 . The clock signal provided by second oscillator  667  is used to operate a real time clock RCLK, and is typically operated using a liquid crystal vibrator  665 . The real time clock is formed as part of bus controller  635  and uses instructions from microprocessor  601  to measure specific elapsed time intervals. As previously indicated, two independent oscillators  663 ,  667 , along with two sets of liquid crystal vibrators  661 ,  665 , are used to make microprocessor  601  clock CLK independent of, and, therefore, independently adjustable from, real time clock RCLK. 
   By making bit d 1  of registers RTCVAL and RTCSEL, for control register  650 , low or high (0 or 1), the real time clock is used to establish four different times or timers. When bit d 0  of register RTCON is set to one, one timer is started. In starting this timer, an interrupt signal is output to microprocessor  601  for a pre-selected timing interval until a zero is written to bit d 0  of register RTCON at which point this timer is stopped. When microprocessor  601  receives this interrupt request signal, it reads register RTCCLR and clears the interrupt request. The output of these interval timers are used for counting user time, etc., during PDL data processing. 
   The configuration of PROM in an exemplary control register  649  is described next. The three registers EEPCS, EEPSK, and EEPDI, shown in  FIG. 18  are contained in PROM register  649  of  FIG. 19 . These registers are typically memory elements built into cartridge  503  which are used to exchange data with EEPROM  670 , which is capable of being electrically erased and rewritten with data. 
   Cartridge  503  stores variables (configuration parameters) required for the operation of laser printer  500  in EEPROM  670  which performs reading, deletion, and rewriting of data using a serial transfer format. An EEPROM found useful in implementing the invention is an EPROM, part number NMC93C66×3, manufactured by National Semiconductor. EEPROM  670  has a memory capacity of around 16 bits by 256 bytes (number of registers) and is capable of reading, erasing or writing the contents of any specified register. When selected using a chip select signal CS, EEPROM  670  receives zero (0) and one (1) value binary data transferred to serial data input terminal Din in synchronization with the serial data clock SL. However, the first three data bits being transferred are interpreted as a command to the EEPROM, and the next eight bits are interpreted as a register number or location for reading, erasing, or writing data. When writing data to be stored, it is supplied to input terminal Din in synchronization with serial data clock SL following the command and register specifications. 
   Register EEPCS provides a signal that switches the level of the chip select signal. When microprocessor  601  writes a zero to bit d 0  of this register, EEPROM  670  is selected. Register EEPSK is used to generate serial clock SK. Microprocessor  601  generates a serial data clock for use by EEPROM  670  by alternately writing zeros and ones to register EEPSK Register EEPDI is used to retain each data bit that is written to EEPROM  670 . When microprocessor  601  generates clock SK by rewriting register EEPSK, it simultaneously rewrites a bit d 0  of register EEPDI based on the data to be rewritten. Data output terminal Dout of EEPROM  670  represents bit d 0  of transfer flag register  647 , which was previously described. After providing a data read command and identification of the register to be read to EEPROM  670 , if microprocessor  601  reads bit d 0  of transfer flag register  647  at the same time as the serial data clock, it reads the contents of the specified register. Since data stored in EEPROM  670  is retained even if power is turned off, the circuit or logic configuration present prior to power loss can be restored by reading the contents of EEPROM  670  immediately after power is restored to laser printer  500 . 
   F. Read Control Circuit Configuration and Operation 
   An exemplary read control circuit  620  and associated data transfer steps utilized in its operation are described next. As shown in  FIG. 23 , read control circuit  620  uses two 8-bit latches, a first latch  651  and a second latch  652 , a ROM  671  to output transferred data, a three-input AND gate  672 , and a D-type flip-flop  674 , which generates flag EWRDY (bit  0 ) of status register  645 . Viewing read control circuit  620  from the point of view of control circuit  501 , as shown in  FIG. 17 , latches  651  and  652  correspond to the two registers EWWRL and EWWRH, which transfer data in 8-bit units. These registers are used to transfer the low end bytes (EWWRL) and high end bytes (EWWRH), respectively, of data in which each word is equal to 16 bits. From the microprocessor  601  point of view, latches  651  and  652  correspond to register EWRD, which is shown in  FIG. 18 . That is, microprocessor  601  can read both latches,  651  and  652 , as one word through data bus DB 29 . 
   ROM  671  of read control circuit  620  typically stores 256 bytes of data and can be realized using a fuse type ROM, a low-capacity PROM, etc., as will be apparent to those skilled in the art Of course it may also be realized by using a portion of a larger-capacity ROM, or a RAM by transferring the data in advance of access. The lower 8 bits (AC 1  to AC 8 ) of the address line from address bus CAB are connected to address terminals A 0  to A 7  of ROM  671 . ROM  671  output data terminals O 0  to O 7  are connected to inputs  1 D to  8 D of first and second latches  651  and  652 . ROM  671  terminals O 0  to O 7  are also connected to FIFO control circuit  623  through data bus lines Z 0  to Z 7  for FIFO control circuit  623 . 
   The outputs of latches  651  and  652 , D 0  to D 7  and D 8  to D 15 , are connected to data bus DB 29 , which is read as register EWRD by microprocessor  601 . A three-input AND gate  672  provides an output signal /EWROM which is input to both a chip select terminal CE and an output enable terminal OE of ROM  671 . When either of the /EWWRH, /FIFOWR, or /EWWRL, signals input to AND gate  672  are at a low logic level, /EWROM is low, OE and CE are driven high, and ROM  671  outputs address data specified by the eight low end bits on address bus CAB. 
   The /EWWRH signal goes low when a higher end byte is selected for transfer by read control circuit  620  and /EWWRL goes low when a lower end byte is selected for transfer. The /FIFOWR signal goes low when data transfer is selected by FIFO control circuit  623 . Since the /EWWRL and /EWWRH signals are input to clock terminals CK of latches  651  and  652 , respectively, data is output from ROM  671  when these signals become active or low, and that data is retained in the latches. Furthermore, because the /EWVVWRL signal is also input to clock terminal C of flip-flop  674 , output Q of flip-flop  674  is inverted to or drops low when lower end bytes are transferred. Output EWRDY is handled as bit d 0  of status register  645 , which has already been described, and bit d 1  of transfer flag register  647 . That is, it is treated as an EWRDY flag. 
   First and second latches  651  and  652  are treated as register EWRD by microprocessor  601 . Therefore, microprocessor  601  carries out a read operation toward the EWRD register when attempting to read data stored in latches  651  and  652 . At this time, the /EWRD signal becomes active low (0) and data retained first is output from latches  651  and  652 , which are connected to the output enable pin. That is, data that was retained first by the latches is output on data bus DB 29 . Because the /EWRD signal is connected to preset terminal PR of flip-flop  674 , at the same time that microprocessor  601  reads data from the latches, the logic level of the EWRDY signal, changes to high. That is, flag EWRDY, which is bit d 0  of the status registers  645  and bit d 1  of the transfer flag registers  647 , is set to a logic level of one. 
   Assuming the above hardware configuration, control circuit  501  and microprocessor  601  transfer data from control circuit  501  to microprocessor  601  using the following procedures. The data to be transferred is the print data that control circuit  501  receives from work station  507 , and the PDL program that is to be implemented by microprocessor  601 . The data transfer accomplished by read control circuit  620 , occurs using the data transfer routine illustrated in  FIG. 24  and executed by CPU  510 , and also using the data read interrupt processing routine shown in  FIG. 26  and executed by microprocessor  601 . 
   When print data has been prepared for transfer to cartridge  503 , the processing routine shown in the flow chart of  FIG. 24  commences. First, flag EWRDY (bit d 0 ) of status register  645  is read in a step S 700  and set to zero when data is transferred into latches  651  and  652 . When that data is read by microprocessor  601 , the EWRDY flag is set to one. Thus, a determination can be made as to whether or not flag EVVRDY is set at one in a subsequent step S 705 . 
   A standby mode is adopted until flag EWRDY is set at a logical one level. When flag EWRDY is one, the next address, which is equal to the first address in the EWWRH area or portion of memory plus twice the amount (number of bytes) of data (Dx2) to be transferred, is read in a step S 710 . When reading takes place for memory area EWWRH, data is read from ROM  671 , and as shown in  FIG. 25 , the 256-byte data, is written sequentially at even number addresses within EWWRH, from 00h to FFh, in ROM  671 . 
   The reason that no data is written to odd address values is because CPU  510  data access takes place in 1 word, or 16-bit, increments. Accessing words beginning with odd address numbers (an element of address bus errors) is not possible. When reading takes place for an address Dx2 away from the first address in area EWWR, data (D) is read from ROM  671  and latched in second latch  652 , as shown in  FIG. 23 . 
   In this manner, when the transfer of higher end bytes of data, as retained by second latch  652 , occurs, CPU  510  transfers the lower end bytes, or data retained by first latch  651 , in a step S 715 . When one word of data has been retained in latches  651  and  652 , CPU  510  sets one of the interrupt request registers (in this embodiment AMDINT 0 ) in a step S 720 . CPU  510  continues execution of the transfer routine shown in  FIG. 24 . However, when the data retention takes place using first latch  651 , flag EWRDY is set low (0), as indicated in  FIG. 23 . Therefore, transfer of the next data does not occur until flag EWRDY is set high (1) as in steps S 700  and S 705 . 
   When CPU  510  sets an interrupt request register (AMDINT 0 ), microprocessor  601  receives this interrupt request and starts a data read interrupt routine as shown in  FIG. 26 . This routine begins immediately after data is retained in latches  651  and  652  of read control circuit  620 . Microprocessor  601  reads the one word of data prepared by control circuit  501  in step S 730  by reading register EWRD. After that, microprocessor  601  transfers the data it read to specified areas of RAMs  611  through  614  (step S 735 ). 
   Using the processing technique described above, electronic control circuit  501  is able to transfer data to cartridge  503 , which is only connected to a read only data bus CDB. Moreover, since data writing takes place in byte sized units and reading takes place in word sized units, microprocessor  601  can more effectively receive data. The embodiment described above transferred data one word at a time as an example, but this is not a necessary limitation and data transfer may also take place in byte sized units. In this latter case, data transfer only uses memory storage area EWWRL and the upper eight (high end) bits of data may be discarded by microprocessor  601 . 
   G. FIFO Control Circuit Configuration and Operation 
   FIFO control circuit  623  uses a latch  657  to temporarily store or latch data to be written to FIFO memory  621 , and FIFO write and read registers  653  and  655 , respectively, to control the writing and reading of data to FIFO memory  621 . FIFO memory  621  typically stores 1,152 bytes of data and has internal write address and read counters. Internally, FIFO memory  621  has a write reset terminal, a read reset terminal, a write 8-bit data bus, a read 8-bit data bus, a write clock terminal, and a read clock terminal, all of which reset respective write and read counters. 
   In order to use FIFO memory  621  to transfer data from control circuit  501  to microprocessor  601 , CPU  510  executes a transfer routine as illustrated in  FIG. 27 , which will be described first, and microprocessor  601  executes a processing routine illustrated in  FIG. 28 . 
   CPU  510  transfers several bytes of data using FIFO control circuit  623 . When the data transfer routine shown in  FIG. 27  is started by CPU  510 , register FIFORST, which belongs to FIFO write circuit  654  of FIFO control circuit  623 , is first read, and an address counter on the write side is also reset in a step S 750 . Next, a variable N is reset to zero in step S 755  and subsequently used to count the number or quantity of data (data words) being transferred. After that, addresses (the first address of register FIFOWR plus data Dx2) are read in a step S 760 . As with read control circuit  620 , when these addresses are read, a specified address in ROM  671  is accessed (see  FIG. 25 ) and data D, which CPU  510  is attempting to transfer, is output and latched using latch  657  through buses Z 0  through Z 7 , which are shown in  FIG. 22 . 
   Next, register FIFOREQ of FIFO control circuit  623  is read, and data D, which is retained in latch  657 , is processed for transfer to FIFO memory  621  in a step S 765 . When register FIFOREQ is read, a write clock is output to the write clock terminal of FIFO memory  621 . Data D, retained in latch  657 , is written to addresses indicated by the write address counter of FIFO memory  621 . At the same time, the contents of the write address counter inside of FIFO memory  621  are incremented by one. After one byte of data is written in this manner, variable N is incremented by one in a step S 770 , and a determination is made in a step S 775  as to whether or not N is equal to a total number of bytes X of data that is to be transferred. As a consequence, steps S 760  to S 775 , are repeated until the number of bytes N of transferred data equals the total number of bytes X of data to be transferred. 
   When the transfer of all of the data is complete, CPU  510  sets one of the interrupt request registers (AMDINT 1 ) and notifies microprocessor  601  that data transfer is complete in a step S 780 . CPU  510  then proceeds through a NEXT step and the data transfer processing routine is terminated. 
   Microprocessor  601  receives interrupt request AMDINT 1  and starts a data receive interrupt routine as represented by the flowchart of  FIG. 28 . When this routine begins, microprocessor  601  first reads register RDRST, which is part of FIFO read register  655  of FIFO control circuit  623 . Microprocessor  601  then resets the address counter on the read side of FIFO memory  621  in a step S 800 . A variable M is then set at zero in a step  805  and subsequently used to count the number or amount of data received. 
   Register FIRCLK, which forms part of FIFO read register  655 , is next read in a step S 810  and data read to specified areas of RAMs  611  through  614  is transferred in a step S 815 . When register FIRCLK is read, a read clock signal is output to the clock terminal on the read side of FIFO memory  621 , and the data D at the address indicated by the read address counter at that time are read out. At the same time, the contents of the address counter on the read side of FIFO memory  621  is incremented by one. Because a PDL program is usually what is being transferred through FIFO control circuit  623 , the received data is transferred immediately to the specific area of RAM to be used for development of image data. 
   When one byte of data is received, variable M is incremented by one in a step S 820 , and whether or not the new value is equal to the total number of bytes X of data to be transferred is determined in a step S 835 . Thus, the processing described above in steps S 810  to S 825  is repeated until the number of bytes M of data received matches the total number of data X to be transferred. 
   When it is determined that data reception or transfer is completed, microprocessor  601  writes a command in polling command register  643  in a step S 630 , to indicate the end of the data reading process. By reading the contents of polling command register  643 , CPU  510  knows that data reception has ended, and microprocessor  601  escapes to the RNT step and ends this processing routine. 
   A significant amount of data can be effectively transferred from control circuit  501  to microprocessor  601  using the processing technique described above. The transferred data is retained in specified areas of RAMs  611  through  614  of data transfer controller  603 , where it awaits processing by microprocessor  601 . When microprocessor  601  receives all of the print data from control circuit  501  that is to be developed (as a program using a PDL), it commences the PDL interpreter stored in ROMs  606  through  609  and processes this print data. Image development takes place using such processing and the results are stored as image data, also in specified areas of RAMs  611  through  614 . 
   H. Double Bank Control Circuit Configuration and Operation 
   The image data provided as a result of image development is transferred to control circuit  501  and stored in a RAM  512  for printing by laser engine  505 . This image data transfer takes place using double bank circuit  624 , which is equipped with two banks that store 32 bytes (16 words) of data each. These banks are referred to as bank A and bank B, and generally have the same hardware construction. Therefore, only an example of the configuration of one bank, bank A, is shown in  FIG. 29 . 
   Each bank is configured to allow selective switching of its address and data buses between connection to microprocessor  601  and control circuit  501 , which occurs for image data transfer. As indicated in  FIG. 29 , two data selectors  681  and  682  are used to select or redirect the address buses. Two sets of octal line buffers are used each set having two buffers, four octal line buffers  684  through  687  total, to select a (16-bit wide) data bus. Two RAMs  691  and  692 , having a 32 byte memory capacity, gates  694  and  695 , here being OR gates, and an inverter  696  complete one bank. In  FIG. 29 , two memory chips with a memory capacity of 32 bytes are used but a single memory chip could be used with appropriate switching of high end addresses. 
   Data selector  682  is configured to select and output the four least significant or low end bits (AC 1  through AC 4 ) from address bus CAB of control circuit  501 , and the four low end bits (A 2  through A 5 ) from microprocessor  601 . Address selection occurs using an ADDMUXA signal (register ADDMUXA bit d 0 ), which is connected to a select terminal S. Data selector  682  switches the read and write signals of RAMs  691  and  692  to match a desired address bus selection, and switches whichever signal is connected to chip select terminals CE 1  and CE 2 , and output enable terminal OE, using the ADDMUXA signal. 
   Octal line buffers  684  and  685  are typically configured as tri-state line buffers and are connected to data bus DB 29 . When gate terminals  1 G and  2 G are set low (0), data bus DB 29  of microprocessor  601  and is connected to the data buses of RAMs  691  and  692 , and data can be written from microprocessor  601  to RAMs  691  and  692 . A two-input OR gate  694  is connected to receive signals /DPWROA and /ADDMUXA as inputs, and has an output connected to both gate terminals  1 G and  2 G of buffers  684  and  685 . The /DPWROA signal goes low (0) when microprocessor  601  attempts to write data to bank A. Therefore, to write data to bank A, if bit d 0  of register ADDMUXA is set low in advance, the gates of line buffers  684  and  685  open and when microprocessor  601  outputs data to bus DB 29 , it is output to the data buses of RAMs  691  and  692  where it is stored. 
   When gate terminals  1 G and  2 G of line buffers  686  and  687  are set low (0), data bus DB 68  is connected to the data buses of RAMs  691  and  692  and data is read from RAMs  691  and  692  to control circuit  501 . A two-input OR gate  695  is connected to receive an inverted signal /DPOE 1 A from an inverter  696  and the ADDMUXA signal as its inputs, and has an output connected to both gate terminals  1 G and  2 G of line buffers  686  and  687 . The /DPOE 1 A signal goes low (0) when control circuit  501  attempts to read data from bank A. Therefore, to read data from bank A, if bit d of register ADDMUXA is set high (1) in advance, the gates of line buffers  686  and  687  are open and data output to the data buses of RAMs  691  and  692  is output to data bus DB 68  when the control circuit  501  performs a read operation. 
   The transfer of image data by microprocessor  601  and receipt by CPU  510  are now described assuming the above type of bank memory hardware. A flowchart illustrating an exemplary transfer initiation routine for image data, which is executed by microprocessor  601 , is shown in  FIG. 30 . As shown in  FIG. 30 , before image data is transferred, microprocessor  601  places a transfer start command in polling command register  643  in a step S 850 , and CPU  510  reads this command and executes the response processing routine illustrated in  FIG. 31 . That is, electronic control circuit  501  determines whether or not laser printer  500  is print enabled in a step S 860 . If laser printer  500  is enabled, one of the interrupt request registers (AMDINT 2 ) is set, in a step S 865 , and operation proceeds to the step labeled NEXT which temporarily terminates the current routine. If, on the other hand, laser printer  500  is not enabled, microprocessor  601  is notified of this status in a step S 870 . If laser printer  500  is not print enabled, it means that the laser printer cannot print even if it receives the image data. For example, laser engine  505  might still not be warmed up or could have a paper jam. 
   When microprocessor  601  receives interrupt request signal AMDINT 2  from control circuit  501 , it starts the transfer interrupt routine shown in  FIG. 31 . When this processing starts, microprocessor  601  first writes a one to bit d 0  of register ADDMUXA as in a step S 900 . When bit d 0  of register ADDMUXA is one, as described using  FIG. 29 , the data buses of RAMs  691  and  692 , which form bank A, are connected to data bus DB 29  of microprocessor  601  and no access from control circuit  501  can take place. 
   Microprocessor  601  then transfers  16  words (here 32 bytes) of data to bank A DPWROA in a step S 902 . When data is written to bank A DPWROA, signal /DPWROA, which is shown in  FIG. 29 , goes low and data is written to RAMs  691  and  692  through line buffers  684  and  685 . When this 16 word data transfer ends, microprocessor  601  writes a one to bit d 0  of register ADDMUXA, in a step S 904 , and connects the data buses of RAMs  691  and  692  to data bus DB 68  of control circuit  501 . 
   After that, microprocessor  601  writes command data to bank A, in a step S 906 , to notify polling command register  643  that data transfer has ended, and data transfer for bank A terminates. Microprocessor  601  next executes the same processing described above for bank B, in a step S 910 . When data transfer for bank B terminates, in the same manner, microprocessor  601  writes additional command data to notify polling command register  643  that this transfer has ended. In this manner, a total of 32 words (or 64 bytes) of data are transferred from cartridge  503  to banks A and B. 
   CPU  510  executes the image data reception routine shown in  FIG. 33  for the microprocessor  601  processing described above. That is, CPU  510  first reads bit d 3  of status register  645  or flag CMDRD in a step S 920  and determines whether or not it is set to zero in a step S 925 . When command data is to be written from microprocessor  601  to polling command register  643 , flag CMDRD is set to zero. At this time, CPU  510  reads the command data in polling command register  643  in a step S 930 . The command data is then checked, in a step S 935 , to determine whether or not it indicates data transfers to bank A have ended, and if not, other processing (step S 940 ) is executed. If the command data of polling command register  643  indicates an end to bank A data transfer, control circuit  501  reads the 16 words of bank A DPRAMA (see  FIG. 17 ) in a step S 945  and transfers the data to RAM  512  in a step S 950 . At this point, the reading of the 16-word data from bank A is terminated. 
   Control circuit  501 , which permits the transfer of the next  16  words from microprocessor  601 , then sets one of the interrupt request registers (AMDINT 2 ), and the processing described above for steps S 920  to S 955  is executed for bank B. That is, when control circuit  501  determines from command data in polling command register  643  that data transfer from microprocessor  601  for bank B has ended, after reading the 16-word data of bank B DPRAMB and transferring it to RAM  512 , it sets one of the interrupt request registers, requesting an interrupt from microprocessor  601 . 
   Since microprocessor  601  repeats the interrupt processing routine shown in  FIG. 32  when it receives such an interrupt request, the transfer of all data terminates when microprocessor  601  and CPU  510  have executed both routines ( FIGS. 32 and 33 ). After the transfer of all of the image data, if new print data is not received from control circuit  501 , microprocessor  601  writes a one in register CLKDIV of control register  650  after a predetermined amount of time and cuts its own operating frequency in half, here to 12.5 MHz, thereby reducing power consumption and generation of undesirable heat. 
   I. Image Data Printing 
   Control circuit  501 , receives and then prints all of the image data by exchanging signals with laser engine  505  using double buffer  520  and a register  517 . The exchange of signals between control circuit  501  and laser engine  505  is illustrated in graphic form in  FIG. 34  and a general description of the printing process is provided below with reference to that figure. 
   When control circuit  501  receives developed image data from cartridge  503 , it determines if laser engine  505  is ready to allow printing, that is, is the printer in a print-enabled mode. After any warm up period has ended and printing is enabled, the signals shown in  FIG. 34  are output to laser engine  505  through register  517 . Laser engine  505  receives these signals and immediately starts a paper or print medium transport motor. At the same time, rotation of the photosensitive drum begins, as does electrostatic charge processing, etc. 
   When paper, or other media, on which printing is to take place reaches a specified position relative to the photosensitive drum, laser engine  505  senses the leading edge of the paper and outputs a vertical margin control or VREQ signal to control circuit  501  through register  517 . Upon receipt of the VREQ signal, control circuit  501  enters a standby mode for a pre-selected period of time. That is, it suspends or delays signal transmission to laser engine  505  for the length of time required for the photosensitive drum to rotate to a starting position for latent image formation, using a laser scanning beam. 
   A vertical synchronization or VSYNC signal is then output through register  517  to laser engine  505  which responds by outputting a laser beam horizontal synchronization or HSYNC signal through register  517 . Because the VSYNC signal is the equivalent of an instruction to start reading one line of image data, laser engine  505  reads image data from one of RAMs  520 A or  520 B, of double bank buffer circuit  520 , in synchronization with the VSYNC signal. To form blank or empty top or bottom margins on the image media, here paper, a controlled interruption or override to ignore the VSYNC signal occurs for the length of time required to scan the number of lines required to form the desired margin. 
   At the same time, CPU  510  counts signals and transfers required image data to RAM  520 A or RAM  520 B of double-buffer circuit  520 . CPU  510  ends this transfer of image data to double buffer  520  when either a specified amount of time has elapsed after detection of a paper trailing edge, or a horizontal synchronization signal count reaches a preset value corresponding to the paper size. Using the above processing steps, one page of image data is transferred to laser engine  505  and then printed on paper. 
   III. Miscellaneous Aspects of the Invention 
   Embodiments of this invention were described above as being applied to printers. However, use of this invention is not limited to printers. The present invention can be applied to all types of equipment the uses an internal processor. For example, dedicated word processors, personal computers, work stations, electronic vehicle devices, facsimile machines, telephones, electronic memos, musical instruments, cameras, translation machines, hand copiers, cash dispensers, remote control devices and electronic calculators which utilize such processors, as well as cartridges of any other information processing device are some of the possible applications. In recent years, such computer related equipment has not only employed expansion slots, but often cartridge type expansion devices, such as IC cards. 
   In dedicated word processors and personal computers, equipped with expansion slots and IC card connectors, improving or adding to data processing functions or making operational modifications can be made easy. Such ease is achieved if the cartridge of this invention is installed in one of these devices and a monitor command, etc., is used to convert the operations of the original equipment processor to processing routines stored in the built in cartridge memory so that the original electronic equipment processor processes data along with the add-on control device. Moreover, if control is switched to a cartridge, no matter what the processing or process steps are, they can be modified. Therefore, it is possible to modify and improve the functionality of existing equipment as well as update software versions in a variety of dedicated equipment, such as dedicated word processors. 
   In this manner, this invention can be applied to all types of data processing equipment that use a processor to which an add-on cartridge or circuit can be connected, such as, for example, electronic automobile parts, facsimile machines, telephones, electronic memos, electronic musical instruments, electronic cameras, electronic translation machines, hand copiers, cash dispensers, remote control devices and electronic calculators. In such data processing equipment, if the processor on the equipment side is able to recognize the cartridge and easily switch its processing to an address provided for the cartridge, it is easy to use the cartridge and data processing device, even on existing electronic devices. If the equipment does not have such functions, a variety of means can be devised to switch the equipment side processor to the processing stored in the cartridge. 
   When a 68000 type microprocessor reads data from a specified address, the equipment or device (referred to as a slave) outputting the data determines whether or not data is on the data bus by using a data acknowledge signal, or DTACK for short. The DTACK signal provides a detectable response for the processor. For this reason, when the processor executes a jump instruction to an absolute address while executing processing routines stored in ROM on the equipment side, the cartridge analyzes and detects whether this was an execution of a jump instruction to an absolute address. The cartridge then outputs the execution address of the built in cartridge ROM to the data bus before the printer ROM outputs the absolute address of the jump destination to the data bus. The cartridge also returns a DTACK signal to the equipment-processor and forces processing to switch to a specified address in the cartridge. Once processing switches to the cartridge ROM, subsequent operations can be configured in a variety of manners. 
   This example assumes that the processor in the target electronic equipment executes a jump instruction to an absolute address. However, it is possible to use a configuration where the jump command itself is read from the equipment ROM. When power is applied and instructions initially read from ROM in the equipment, a code equivalent to a jump instruction from the cartridge is placed on the data bus, and signal DTACK is returned. While these methods raise the danger of a DTACK conflict, a detailed analysis of bus timing and appropriate design makes them possible to realize. 
   In addition, as shown in  FIG. 35 , slots or holes may be formed in printed circuit board  550  where compressible material  126  is located so that it presses directly against microprocessor  601 . This configuration increases heat dissipation by also transferring heat directly through material  126 . However, in some applications compressible material piece  126  may be omitted because printed circuit board  550  is itself manufactured from a substantially flexible material or plastic, and microprocessor  601  can be pushed or pressed upward using the elasticity of printed circuit board  550  itself with an appropriately physically biased mounting technique. 
   As indicated in  FIG. 35 , that portion of upper casing  100  making contact with microprocessor  601  is generally slightly raised ( 104 ). However, if the top surface of microprocessor  601  is made higher than the top of other circuit devices or components on the same side of printed circuit board  550 , it is not necessary to raise area  104  to place the top of microprocessor  601  in contact with the casing. However, providing raised area  104  also allows accommodation of some unevenness in the inner surface of upper casing  100 , which in turn advantageously allows upper casing  100  to be manufactured easily using die casting or hand processing techniques. 
   In the above embodiments, microprocessor  601  is mounted approximately along a center line and to the front of the cartridge along the direction in which the cartridge is inserted. However, if one or more other circuit elements within the cartridge generate more heat than microprocessor  601 , they may be placed approximately centered and toward the front, connector end, of the cartridge. That is, it is generally better to place circuit elements or devices that generate the most heat centered in the front of the cartridge, regardless of their ultimate function. This allows the advantages of more efficient cooling through various conductive and convective dissipation techniques to be applied to the largest sources of heat in the cartridge to fully realize the potential of the inventive technique and apparatus. 
   This invention is not limited in any manner to the embodiments described above. It is possible to implement this invention in a variety of forms that do not deviate from the teachings of this invention. For example, the cartridge could have a built in outline font and receive data on the character point size from the printer and then generate a bit image at the designated point size and transfer it to the printer. The cartridge could be configured to store and display, without performing especially intricate processing, data received from the electronic device. The printer could also be of the ink-jet variety. 
   While the invention has been described in conjunction with several specific embodiments, it is evident to those skilled in the art that many further alternatives, modifications and variations will be apparent in light of the foregoing description. Thus, the invention described herein is intended to embrace all such alternatives, modifications, applications and variations as may fall within the spirit and scope of the appended claims. 
   
     
       
             
           
             
             
             
           
         
             
               APPENDIX A 
             
             
                 
             
             
               NUMERICAL FIGURE DESIGNATIONS 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
                 
                1 
               First main printer 
             
             
                 
                1A 
               Second main printer 
             
             
                 
                1B 
               Third main printer 
             
             
                 
                15 
               Xerography unit 
             
             
                 
                27 
               Ink supply 
             
             
                 
               100 
               Upper case 
             
             
                 
               102 
               Heat dissipation material 
             
             
                 
               104 
               Spring 
             
             
                 
               106 
               Expansion memory slot 
             
             
                 
               108 
               Cartridge End 
             
             
                 
               110 
               Metal plate 
             
             
                 
               120 
               Lower case 
             
             
                 
               121 
               Plate 
             
             
                 
               122 
               Spring elements 
             
             
                 
               122a 
               First curved extension 
             
             
                 
               122b 
               Second curved extension 
             
             
                 
               124 
               Mating wall 
             
             
                 
               125 
               Screw hole 
             
             
                 
               126 
               Biasing element 
             
             
                 
               128 
               Biasing element retainer 
             
             
                 
               132 
               Opening 
             
             
                 
               140 
               Lower cap 
             
             
                 
               141 
               Cap mounting tabs 
             
             
                 
               142 
               Through-hole 
             
             
                 
               150 
               Upper cap 
             
             
                 
               152 
               Button lock 
             
             
                 
               154 
               Button lock springs 
             
             
                 
               160 
               Screws 
             
             
                 
               180 
               First printer frame 
             
             
                 
               182 
               Second printer frame 
             
             
                 
               200 
               IC card 
             
             
                 
               210 
               IC card connector 
             
             
                 
               500 
               Printer 
             
             
                 
               501 
               Electronic control circuit 
             
             
                 
               503 
               Cartridge 
             
             
                 
               505 
               Laser engine 
             
             
                 
               507 
               Workstation 
             
             
                 
               510 
               CPU 
             
             
                 
               511 
               ROM 
             
             
                 
               512 
               RAM 
             
             
                 
               514 
               Data input port 
             
             
                 
               515 
               Line buffer 
             
             
                 
               516 
               Bus line 
             
             
                 
               517 
               Register 
             
             
                 
               518 
               Console panel 
             
             
                 
               519 
               Console panel I/F 
             
             
                 
               520 
               Double-buffer circuit 
             
             
                 
               520A 
               RAM 
             
             
                 
               520B 
               RAM 
             
             
                 
               520C 
               Memory write controller 
             
             
                 
               520D 
               Memory read controller 
             
             
                 
               550 
               Printed circuit board 
             
             
                 
               551 
               Plug 
             
             
                 
               560 
               First contact pad set 
             
             
                 
               562 
               Second contact pad set 
             
             
                 
               564 
               Third contact pad set 
             
             
                 
               566 
               Fourth contact pad 
             
             
                 
               570 
               Chain 
             
             
                 
               572 
               Reinforced passage 
             
             
                 
               573 
               Ring 
             
             
                 
               574 
               Printer ground terminal 
             
             
                 
               580 
               Keyed lock mechanism 
             
             
                 
               582 
               Protruding element 
             
             
                 
               601 
               Microprocessor 
             
             
                 
               601p 
               Microprocessor pins 
             
             
                 
               602 
               Memory 
             
             
                 
               603 
               Data transfer controller 
             
             
                 
               606 
               ROM 
             
             
                 
               607 
               ROM 
             
             
                 
               608 
               ROM 
             
             
                 
               609 
               ROM 
             
             
                 
               610 
               Data selector 
             
             
                 
               611 
               RAM 
             
             
                 
               612 
               RAM 
             
             
                 
               613 
               RAM 
             
             
                 
               614 
               RAM 
             
             
                 
               615 
               Expansion RAM interface 
             
             
                 
               617 
               Tri-state buffer 
             
             
                 
               618 
               ROM 
             
             
                 
               619 
               Tri-state data buffer 
             
             
                 
               620 
               Read control circuit 
             
             
                 
               621 
               FIFO memory 
             
             
                 
               623 
               FIFO control circuit 
             
             
                 
               624 
               Double-buffer control circuit 
             
             
                 
               631 
               First decoder 
             
             
                 
               632 
               Second decoder 
             
             
                 
               635 
               Bus controller 
             
             
                 
               637 
               Reset terminal 
             
             
                 
               640 
               Interrupt request register 
             
             
                 
               640a 
               First D-type flip-flop 
             
             
                 
               640b 
               Second D-type flip-flop 
             
             
                 
               640c 
               Third D-type flip-flop 
             
             
                 
               643 
               Command register 
             
             
                 
               643a 
               First octal D-type flip-flop 
             
             
                 
               643b 
               Second octal D-type flip-flop 
             
             
                 
               643c 
               Fourth D-type flip-flop 
             
             
                 
               645 
               Status register 
             
             
                 
               647 
               Transfer flag register 
             
             
                 
               649 
               PROM control register 
             
             
                 
               650 
               Control register 
             
             
                 
               651 
               First latch 
             
             
                 
               652 
               Second latch 
             
             
                 
               653 
               FIFO register 
             
             
                 
               654 
               FIFO write circuit 
             
             
                 
               655 
               FIFO read register 
             
             
                 
               657 
               FIFO latch 
             
             
                 
               658 
               First double bank buffer 
             
             
                 
               659 
               Second double bank buffer 
             
             
                 
               661 
               First oscillator 
             
             
                 
               663 
               First oscillator 
             
             
                 
               665 
               Second oscillator 
             
             
                 
               667 
               Second oscillator 
             
             
                 
               670 
               EEPROM 
             
             
                 
               671 
               ROM 
             
             
                 
               674 
               Fifth D-type flip-flop 
             
             
                 
               680 
               NAND gate 
             
             
                 
               681 
               First data selector 
             
             
                 
               682 
               Second data selector 
             
             
                 
               684 
               First tri-state buffer 
             
             
                 
               685 
               Second tri-state buffer 
             
             
                 
               686 
               Third tri-state buffer 
             
             
                 
               687 
               Fourth tri-state buffer 
             
             
                 
               691 
               RAM 
             
             
                 
               692 
               RAM 
             
             
                 
               694 
               First OR gate 
             
             
                 
               695 
               Second OR gate 
             
             
                 
               696 
               Inverter 
             
             
                 
               AAB 
               Microprocessor address bus 
             
             
                 
               CAB 
               Connector address bus 
             
             
                 
               CCC 
               Control signal 
             
             
                 
               CDB 
               Data bus 
             
             
                 
               CLK 
               Clock signal 
             
             
                 
               CN10 
               Printer connector 
             
             
                 
               CN11 
               Add-on connector 
             
             
                 
               CSEL 
               Cartridge selector signals 
             
             
                 
               DB29 
               Data bus 
             
             
                 
               DB68 
               Data selector bus 
             
             
                 
               EAB 
               Expansion address bus 
             
             
                 
               IDB 
               ROM 606 to 609 data bus 
             
             
                 
               RCLK 
               Real time clock signal