# Patent

## Title
Method and system for collecting servo field data from programmable devices in embedded disk controllers

## Abstract

A system for collecting servo field data from programmable devices in embedded disk controllers. The system includes a servo controller with a read channel interface. The read channel interface includes a programmable control logic that receives a servo field detected signal from a module that detects a servo field start bit; and a register in the read channel interface that is enabled by the programmable control logic for receiving servo field data from a read channel device. The programmable control logic is configured to operate both in a two wire mode and in a three wire mode allowing the servo controller to process servo data from the read channel device.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This is application is related to the following U.S. patent applications, filed on even date herewith and incorporated herein by reference in entirety;
“METHOD AND SYSTEM FOR AUTOMATIC TIME BASE ADJUSTMENT FOR DISK DRIVE SERVO CONTROLLERS”, Ser. No. 10/384,992, with Michael Spaur and Raymond A. Sandoval as inventors.
“METHOD AND SYSTEM FOR EMBEDDED DISK CONTROLLERS”, Ser. No. 10/385,022 with Larry L. Byers, Paul B. Ricci, Joseph G. Kriscunas, Joseba M. Desubijana, Gary R. Robeck, David M. Purdham and Michael R. Spaur as inventors.
“METHOD AND SYSTEM FOR USING AN INTERRUPT CONTROLLER IN EMBEDDED DISK CONTROLLERS”, Ser. No. 10/384,991, with David M. Purdham, Larry L. Byers and Andrew Artz as inventors.
“METHOD AND SYSTEM FOR MONITORING EMBEDDED DISK CONTROLLER COMPONENTS”, Ser. No. 10/385,042, with Larry L. Byers, Joseba M. Desubijana, Gary R. Robeck, and William W. Dennin as inventors.
“METHOD AND SYSTEM FOR SUPPORTING MULTIPLE EXTERNAL SERIAL PORT DEVICES USING A SERIAL PORT CONTROLLER IN EMBEDDED DISK CONTROLLERS”, Ser. No. 10/385,039, with Michael Spaur and Ihn Kim as inventors.
“METHOD AND SYSTEM FOR USING AN EXTERNAL BUS CONTROLLER IN EMBEDDED DISK CONTROLLERS” Ser. No. 10/385,056, with GARY R. ROBECK, LARRY L. BYERS, JOSEBA M. DESUBIJANA, And FREDARICO E. DUTTON as inventors.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to storage systems, and more particularly to disk drive servo controllers.
2. Background
Conventional computer systems typically include several functional components. These components may include a central processing unit (CPU), main memory, input/output (“I/O”) devices, and disk drives. In conventional systems, the main memory is coupled to the CPU via a system bus or a local memory bus. The main memory is used to provide the CPU access to data and/or program information that is stored in main memory at execution time. Typically, the main memory is composed of random access memory (RAM) circuits. A computer system with the CPU and main memory is often referred to as a host system.
The main memory is typically smaller than disk drives and may be volatile. Programming data is often stored on the disk drive and read into main memory as needed. The disk drives are coupled to the host system via a disk controller that handles complex details of interfacing the disk drives to the host system. Communications between the host system and the disk controller is usually provided using one of a variety of standard I/O bus interfaces.
Typically, a disk drive includes one or more magnetic disks. Each disk (or platter) typically has a number of concentric rings or tracks (platter) on which data is stored. The tracks themselves may be divided into sectors, which are the smallest accessible data units. A positioning head above the appropriate track accesses a sector. An index pulse typically identifies the first sector of a track. The start of each sector is identified with a sector pulse. Typically, the disk drive waits until a desired sector rotates beneath the head before proceeding with a read or writes operation. Data is accessed serially, one bit at a time and typically, each disk has its own read/write head.
FIG. 1 shows a disk drive system 100 with platters 101A and 101B, an actuator 102 and read/write head 103. Typically, multiple platters/read and write heads are used. Platters 101A–101B have assigned tracks for storing system information, servo data and user data.
The disk drive is connected to the disk controller that performs numerous functions, for example, converting digital to analog data signals, disk formatting, error checking and fixing, logical to physical address mapping and data buffering. To perform the various functions for transferring data, the disk controller includes numerous components.
To access data from a disk drive (or to write data), the host system must know where to read (or write data to) the data from the disk drive. A driver typically performs this task. Once the disk drive address is known, the address is translated to cylinder, head and sector, based on platter geometry and sent to the disk controller. Logic on the hard disk looks at the number of cylinders requested. Servo controller firmware instructs motor control hardware to move read/write heads 103 to the appropriate track. When the head is in the correct position, it reads the data from the correct track.
Typically, read and write head 103 has a write core for writing data in a data region, and a read core for magnetically detecting the data written in the data region of a track and a servo pattern recorded on a servo region.
A servo system 104 detects the position of head 103 on platter 101A according to the phase of a servo pattern detected by the read core of head 103. Servo system 104 then moves head 103 to the target position.
Servo system 104 servo-controls head 103 while receiving feedback for a detected position obtained from a servo pattern so that any positional error between the detected position and the target position is negated.
Typically, a servo controller in system 104 communicates with a data recovery device. One such device is shown in FIG. 3, as the “read channel device 303”. An example of such a product is “88C7500 Integrated Read channel” device sold by Marvell Semiconductor Inc®.
Typically, servo information is recorded in fixed amounts for a given product. In conventional systems, all the elements of servo fields are “hard-wired” to include details of interface timing between the servo controller and the read channel device 303. The conventional approach has drawbacks. For example, the servo controller design must be modified each time the format of any of the servo data elements changes. Also, if the interface between the read channel device 303 and servo controller (303A, FIG. 4) changes, the servo controller must be modified.
Therefore, what is desired is an efficient controller that can accommodate multiple interfaces and also future changes in servo field formats.
SUMMARY OF THE INVENTION
In one aspect of the present invention, a system for collecting servo field data from programmable devices in embedded disk controllers is provided. The system includes, a programmable control logic that receives a servo field detected signal from another module that detects a servo field start bit; and
a register that is enabled by the programmable control logic for receiving servo field data from a programmable device. The programmable control logic may be configured to operate in a three wire or two wire mode.
In another aspect of the present invention, a method for collecting servo field data from programmable devices in embedded disk controllers is provided. The method includes, receiving servo field detection signal; receiving control signal for capturing servo field data; and organizing servo field data.
In one aspect of the present invention, elements of the servo fields are programmable and can be adjusted by firmware. Hence, hardware changes are not required to keep up with format changes.
In another aspect of the present invention, either two or three wire systems may be used without needing any additional circuits.
This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following detailed description of the preferred embodiments thereof in connection with the attached drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing features and other features of the present invention will now be described. In the drawings, the same components have the same reference numerals. The illustrated embodiment is intended to illustrate, but not to limit the invention. The drawings include the following Figures:
FIG. 1 shows a block diagram of a disk drive;
FIG. 2 is a block diagram of an embedded disk controller system, according to one aspect of the present invention;
FIG. 3 is a block diagram showing the various components of the FIG. 3 system and a two-platter, four-head disk drive, according to one aspect of the present invention;
FIG. 4 is a block diagram of a servo controller, according to one aspect of the present invention;
FIG. 5 is a block diagram of a read channel interface, according to one aspect of the present invention;
FIGS. 6A and 6B are timing diagrams for two-wire and three-wire interface systems, respectively, according to one aspect of the present invention; and
FIG. 7 shows a flow diagram of executable process steps, according to one aspect of the present invention.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
To facilitate an understanding of the preferred embodiment, the general architecture and operation of an embedded disk controller will be described initially. The specific architecture and operation of the preferred embodiment will then be described.
FIG. 2 shows a block diagram of an embedded disk controller system 200 according to one aspect of the present invention. System 200 may be an application specific integrated circuit (“ASIC”).
System 200 includes a microprocessor (“MP”) 201 that performs various functions described below. MP 201 may be a Pentium® Class processor designed and developed by Intel Corporation® or an ARM processor. MP 201 is operationally coupled to various system 200 components via buses 222 and 223. Bus 222 may be an Advanced High performance (AHB) bus as specified by ARM Inc. Bus 223 may an Advanced Peripheral Bus (“APB”) as specified by ARM Inc. The specifications for AHB and APB are incorporated herein by reference in their entirety.
System 200 is also provided with a random access memory (RAM) or static RAM (SRAM) 202 that stores programs and instructions, which allows MP 201 to execute computer instructions. MP 201 may execute code instructions (also referred to as “firmware”) out of RAM 202.
System 200 is also provided with read only memory (ROM) 203 that stores invariant instructions, including basic input/output instructions.
System 200 is also provided with a digital signal processor (“DSP”) 206 that controls and monitors various servo functions through DSP interface module (“DSPIM”) 208 and servo controller interface 210 operationally coupled to a servo controller (“SC”)211.
DSPIM 208 interfaces DSP 206 with MP 201 and allows DSP 206 to update a tightly coupled memory module (TCM) 205 (also referred to as “memory module” 205) with servo related information. MP 201 can access TCM 205 via DSPIM 208.
Servo controller interface (“SCI”) 210 includes an APB interface 213 that allows SCI 210 to interface with APB bus 223 and allows SC 211 to interface with MP 201 and DSP 206.
SCI 210 also includes DSPAHB interface 214 that allows access to DSPAHB bus 209. SCI 210 is provided with a digital to analog and analog to digital converter 212 that converts data from analog to digital domain, and vice-versa. Analog data 220 enters module 212 and leaves as analog data 220A to a servo device 221.
SC 211 has a read channel device (RDC) serial port 217, a motor control (“SVC”) serial port 218 for a “combo” motor controller device, a head integrated circuit (HDIC) serial port 219 and a servo data (“SVD”) interface 216 for communicating with various devices.
FIG. 3 shows a block diagram with disk 100 coupled to system 200, according to one aspect of the present invention. FIG. 3 shows a read channel device 303 that receives signals from a pre-amplifier 302 (also known as head integrated circuit (HDIC)) coupled to disk 100. As discussed above, one example of a read channel device 303 is manufactured by Marvell Semiconductor Inc.®, Part Number 88C7500, while pre-amplifier 302 may be a Texas instrument, Part Number SR1790. Pre-amplifier 302 is also operationally coupled to SC 211. Servo data (“SVD”) 305 is sent to SC 211.
A motor controller 307 (also referred to as device 307), (for example, a motor controller manufactured by Texas Instruments®, Part Number SH6764) sends control signals 308 to control actuator movement using motor 307A. It is noteworthy that spindle 101C is controlled by a spindle motor (not shown) for rotating platters 101A and 101B. SC 211 sends plural signals to motor controller 307 including clock, data and “enable” signals to motor controller 307 (for example, SV_SEN, SV_SCLK and SV_SDAT).
SC 211 is also operationally coupled to a piezo controller 509 that allows communication with a piezo device (not shown). One such piezo controller is sold by Rolm Electronics®, Part Number BD6801FV. SC 211 sends clock, data and enable signals to controller 509 (for example, SV_SEN, SV_SCLK and SV_SDAT).
FIG. 4 shows a block diagram of SC 211, according to one aspect of the present invention. FIG. 4 shows SC 211 with a serial port controller 404 for controlling various serial ports 405–407.
SC 211 also has a servo-timing controller (“STC”) 401 that automatically adjusts the time base when a head change occurs. Servo controller 211 includes an interrupt controller 411 that can generate an interrupt to DSP 206 and MP 201. Interrupts may be generated when a servo field is found (or not found) and for other reasons. SC 211 includes a servo monitoring port 412 that monitors various signals to SC 211.
SC 211 uses a pulse width modulation unit (“PWM”) 413 for supporting control of motor 307A PWM, and a spindle motor PWM 409 and a piezo PWM 408.
MP 201 and/or DSP 206 use read channel device 303 for transferring configuration data and operational commands through SC 211 (via read channel interface 303A).
FIG. 5 is a block diagram of read channel interface (also referred to as Interface 303A) 303A. Serial data (505 and 506) from read channel device 303 is sent to serial register 503 and a start detect module 500. Start detect module 500 sends a signal 516 to a counter 501 and control logic 502. Signal 516 is generated after a servo field start bit is detected.
Control logic 502 includes a state machine (not shown) that may be configured by signal 515. Signal 515 includes gray code, Position Error Signal (“PES”), run out correction (“ROC”) and Recovered Service field (“RSF”) configuration information. As is well known in the art, gray code is the front portion of the data as read from a media. MP 201 or DSP 206 may send signal 515.
Servo field search signal 514 is received from DSP 206 or from timer hardware, by a synchronizer 505. Signal 514 indicates the time to begin the search for servo field data. Synchronizer 505 then synchronizes signal 514 with serial data clock 512. Synchronized signal 513 and serial data clock 512 are sent to control logic 502.
Control logic generates signal 510 that is sent to serial register 503. Signal 510 enables serial register 503 to receive data from read channel device 303. Serial register 503 transfers unfiltered data 507 to a bitmap filter 504 that filters data 507 to generate servo data 508 that can be read by DSP 206 or MP 201. DSP 206 or MP 201 using firmware and through signal 509 may set filter 504.
Control logic 502 can operate under plural modes by using signal 511. For example, control logic 502 may operate under a two-wire mode (one clock/one data) or three-wire mode (one clock/two data). Control logic 502 also sends a signal 518 to start detect module 500 that requests start detect module 500 to look for servo data.
FIGS. 6A and 6B show timing diagrams for two-wire and three-wire systems, according to one aspect of the present invention.
FIG. 7 is a flow diagram of executable process steps, according to one aspect of the present invention.
In step S701, serial register 503 receives clock signal 512 and serial data (505 and 506).
In step S700, control logic 502 receives control signal 515 from MP 201 and/or DSP 206. Signal 515 includes gray code, PES, ROC and RSF configuration information.
In step S702, control logic 502 generates signal 510 that enables serial register to capture data.
In step S703, data is organized so that MP 201 and/or DSP 206 can read it. In one aspect, unfiltered servo data 507 is sent to a bit map filter 504 that filters the data and generates servo data 508 so that it can be read by DSP 206 or MP 201.
In one aspect of the present invention, elements of the servo fields are programmable and can be adjusted by firmware. Hence, hardware changes are not required to keep up with format changes. In another aspect of the present invention, both two and three wire systems may be used without using any additional circuits.
Although the present invention has been described with reference to specific embodiments, these embodiments are illustrative only and not limiting. For example, the term signal as used herein includes commands. Many other applications and embodiments of the present invention will be apparent in light of this disclosure and the following claims.

## Claims

1. A system for collecting servo field data from programmable devices in embedded disk controllers, comprising:
a servo controller with a read channel interface wherein the read channel interface comprising: a programmable control logic that receives a servo field detected signal from a module that detects a servo field start bit; and a register in the read channel interface that is enabled by the programmable control logic for receiving servo field data from a read channel device, wherein the programmable control logic is configured to operate both in a two wire mode and in a three wire mode, allowing the servo controller to process servo data from the read channel device.

2. The system of claim 1, further comprising:
a filter that receives unfiltered servo data from the register.

3. The system of claim 1, further comprising:
a counter that receives the servo field detected signal.

4. The system of claim 1, wherein the programmable control logic may be configured by a processor in the embedded disk controller.

5. A method for collecting servo field data from programmable devices in embedded disk controllers, comprising:
receiving a servo field detection signal, wherein the servo field detection signal is received by a programmable control logic in a read channel interface in a servo controller and the programmable control logic is configured to operate both in a two wire mode and in a three wire mode, allowing the servo controller to process servo data from a read channel device;

receiving control signal for capturing servo field data; and
organizing servo field data.

6. The method of claim 5, wherein the programmable control logic in the read channel interface receives the servo field detection signal from a detect module.

7. The method of claim 5, wherein a register in the read channel interface receives the control signal from the programmable control logic.

8. The method of claim 7, wherein the register sends unfiltered servo field data to a bitmap filter.

9. A servo controller for embedded disk controllers, comprising:
a read channel interface that includes a programmable control logic that receives a servo field detected signal from a module that detects a servo field start bit; and
a register in the read channel interface that is enabled by the programmable control logic for receiving servo field data from a read channel device, wherein the programmable control logic is configured to operate both in a two wire mode and in a three wire mode, allowing the servo controller to process servo data from the read channel device.

10. The servo controller of claim 9, further comprising:
a filter that receives unfiltered servo data from the register.

11. The servo controller of claim 9, further comprising:
a counter that receives the servo field detected signal.

12. The servo controller of claim 9, wherein the programmable control logic may be configured by a processor in the embedded disk controller.