Patent Document

CROSS REFERENCE TO RELATED PATENTS/PATENT APPLICATIONS 
   Provisional Priority Claims 
   The present U.S. Utility Patent Application claims priority pursuant to 35 U.S.C. § 119(e) to the following U.S. Provisional Patent Application which is hereby incorporated herein by reference in its entirety and made part of the present U.S. Utility Patent Application for all purposes: 
   U.S. Provisional Application Ser. No. 60/764,132, entitled “Clocking Chien searching at different frequency than other Reed-Solomon (RS) ECC decoding functions,” (Attorney Docket No. BP5087), filed Feb. 1, 2006, pending. 

   BACKGROUND OF THE INVENTION 
   1. Technical Field of the Invention 
   The invention relates generally to memory storage devices; and, more particularly, it relates to error correction coding implemented within such memory storage devices. 
   2. Description of Related Art 
   As is known, many varieties of memory storage devices (e.g. disk drives), such as magnetic disk drives are used to provide data storage for a host device, either directly, or through a network such as a storage area network (SAN) or network attached storage (NAS). Typical host devices include stand alone computer systems such as a desktop or laptop computer, enterprise storage devices such as servers, storage arrays such as a redundant array of independent disks (RAID) arrays, storage routers, storage switches and storage directors, and other consumer devices such as video game systems and digital video recorders. These devices provide high storage capacity in a cost effective manner. 
   Within such hard disk drives (HDDs), error correction coding (ECC) is sometimes employed to ensure the ability to correct for errors of data that is written to and read from the storage media of a HDD. The ECC allows the ability to correct for those errors within the error correction capability of the code. In certain ECC schemes, certain of the calculations and/or processed performed during the decoding processing are much more intensive than others. One prior art approach to deal with this problem is to design a device such that efficiency can be achieved in terms of the particular architecture of the device. However, these schemes tend to be very space/area consumptive within the device, and as such, very costly. This high cost is not only in terms of the actual cost to manufacture the device, but also in terms of other performance parameters such as high power consumption. This can come at the expense of the requisite energy required for other modules and/or processes within the device. Within battery powered devices (e.g., laptop computers when operating on battery power, hand-held devices, etc.) this can be extremely deleterious in terms of performance. 
   There exists a need in the art for a better, more efficient means of performing error correction decoding within such devices. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is directed to apparatus and methods of operation that are further described in the following Brief Description of the Several Views of the Drawings, the Detailed Description of the Invention, and the claims. Other features and advantages of the present invention will become apparent from the following detailed description of the invention made with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  illustrates an embodiment of a disk drive unit. 
       FIG. 2  illustrates an embodiment of a disk controller. 
       FIG. 3A  illustrates an embodiment of a handheld audio unit. 
       FIG. 3B  illustrates an embodiment of a computer. 
       FIG. 3C  illustrates an embodiment of a wireless communication device. 
       FIG. 3D  illustrates an embodiment of a personal digital assistant (PDA). 
       FIG. 3E  illustrates an embodiment of a laptop computer. 
       FIG. 4  illustrates an embodiment of an apparatus that includes a Reed-Solomon (RS) decoder employing two different clock signals. 
       FIG. 5  illustrates an alternative embodiment of an apparatus that includes a RS decoder employing two different clock signals. 
       FIG. 6  illustrates an embodiment of an apparatus that employs two clock tree synthesis modules. 
       FIG. 7  illustrates an embodiment of a RS decoder that performs at least Chien searching. 
       FIG. 8  illustrates an embodiment of a method that performs RS decoding. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  illustrates an embodiment of a disk drive unit  100 . In particular, disk drive unit  100  includes a disk  102  that is rotated by a servo motor (not specifically shown) at a velocity such as 3600 revolutions per minute (RPM), 4200 RPM, 4800 RPM, 5,400 RPM, 7,200 RPM, 10,000 RPM, 15,000 RPM, however, other velocities including greater or lesser velocities may likewise be used, depending on the particular application and implementation in a host device. In one possible embodiment, disk  102  can be a magnetic disk that stores information as magnetic field changes on some type of magnetic medium. The medium can be a rigid or non-rigid, removable or non-removable, that consists of or is coated with magnetic material. 
   Disk drive unit  100  further includes one or more read/write heads  104  that are coupled to arm  106  that is moved by actuator  108  over the surface of the disk  102  either by translation, rotation or both. A disk controller  130  is included for controlling the read and write operations to and from the drive, for controlling the speed of the servo motor and the motion of actuator  108 , and for providing an interface to and from the host device. 
     FIG. 2  illustrates an embodiment of a disk controller  130 . Disk controller  130  includes a read channel  140  and write channel  120  for reading and writing data to and from disk  102  through read/write heads  104 . Disk formatter  125  is included for controlling the formatting of disk drive unit  100 , timing generator  110  provides clock signals and other timing signals, device controllers  105  control the operation of drive devices  109  such as actuator  108  and the servo motor, etc. Host interface  150  receives read and write commands from host device  50  and transmits data read from disk  102  along with other control information in accordance with a host interface protocol. In one possible embodiment of, the host interface protocol can include, SCSI, SATA, enhanced integrated drive electronics (EIDE), or any number of other host interface protocols, either open or proprietary, that can be used for this purpose. 
   Disk controller  130  further includes a processing module  132  and memory module  134 . Processing module  132  can be implemented using one or more microprocessors, micro-controllers, digital signal processors (DSPs), microcomputers, central processing units (CPUs), field programmable gate arrays (FPGAs), programmable logic devices (PLAs), state machines, logic circuits, analog circuits, digital circuits, and/or any devices that manipulates signal (analog and/or digital) based on operational instructions that are stored in memory module  134 . When processing module  132  is implemented with two or more devices, each device can perform the same steps, processes or functions in order to provide fault tolerance or redundancy. Alternatively, the function, steps and processes performed by processing module  132  can be split between different devices to provide greater computational speed and/or efficiency. 
   Memory module  134  may be a single memory device or a plurality of memory devices. Such a memory device may be a read-only memory (ROM), random access memory (RAM), volatile memory, non-volatile memory, static random access memory (SRAM), dynamic random access memory (DRAM), flash memory, cache memory, and/or any device that stores digital information. Note that when the processing module  132  implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory module  134  storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. Further note that, the memory module  134  stores, and the processing module  132  executes, operational instructions that can correspond to one or more of the steps or a process, method and/or function illustrated herein. 
   Disk controller  130  includes a plurality of modules, in particular, device controllers  105 , processing timing generator  110 , processing module  132 , memory module  134 , write channel  120 , read channel  140 , disk formatter  125 , and host interface  150  that are interconnected via bus  136 . Each of these modules can be implemented in hardware, firmware, software or a combination thereof, in accordance with the broad scope of the present invention. While the particular bus architecture is shown in  FIG. 2  with a single bus  136 , alternative bus architectures that include additional data buses, further connectivity, such as direct connectivity between the various modules, are likewise possible to implement additional features and functions. 
   In one possible embodiment, one or more modules of disk controller  130  are implemented as part of a system on a chip (SOC) integrated circuit. In such a possible embodiment, this SOC integrated circuit includes a digital portion that can include additional modules such as protocol converters, linear block code encoding and decoding modules, etc., and an analog portion that includes device controllers  105  and optionally additional modules, such as a power supply, etc. In an alternative embodiment, the various functions and features of disk controller  130  are implemented in a plurality of integrated circuit devices that communicate and combine to perform the functionality of disk controller  130 . 
     FIG. 3A  illustrates an embodiment of a handheld audio unit  51 . In particular, disk drive unit  100  can be implemented in the handheld audio unit  51 . In one possible embodiment, the disk drive unit  100  can include a small form factor magnetic hard disk whose disk  102  has a diameter 1.8″ or smaller that is incorporated into or otherwise used by handheld audio unit  51  to provide general storage or storage of audio content such as motion picture expert group (MPEG) audio layer  3  (MP3) files or Windows Media Architecture (WMA) files, video content such as MPEG4 files for playback to a user, and/or any other type of information that may be stored in a digital format. 
     FIG. 3B  illustrates an embodiment of a computer  52 . In particular, disk drive unit  100  can be implemented in the computer  52 . In one possible embodiment, disk drive unit  100  can include a small form factor magnetic hard disk whose disk  102  has a diameter 1.8″ or smaller, a 2.5″ or 3.5″ drive or larger drive for applications such as enterprise storage applications. Disk drive  100  is incorporated into or otherwise used by computer  52  to provide general purpose storage for any type of information in digital format. Computer  52  can be a desktop computer, or an enterprise storage devices such a server, of a host computer that is attached to a storage array such as a redundant array of independent disks (RAID) array, storage router, edge router, storage switch and/or storage director. 
     FIG. 3C  illustrates an embodiment of a wireless communication device  53 . In particular, disk drive unit  100  can be implemented in the wireless communication device  53 . In one possible embodiment, disk drive unit  100  can include a small form factor magnetic hard disk whose disk  102  has a diameter 1.8″ or smaller that is incorporated into or otherwise used by wireless communication device  53  to provide general storage or storage of audio content such as motion picture expert group (MPEG) audio layer  3  (MP3) files or Windows Media Architecture (WMA) files, video content such as MPEG4 files, JPEG (joint photographic expert group) files, bitmap files and files stored in other graphics formats that may be captured by an integrated camera or downloaded to the wireless communication device  53 , emails, webpage information and other information downloaded from the Internet, address book information, and/or any other type of information that may be stored in a digital format. 
   In a possible embodiment, wireless communication device  53  is capable of communicating via a wireless telephone network such as a cellular, personal communications service (PCS), general packet radio service (GPRS), global system for mobile communications (GSM), and integrated digital enhanced network (iDEN) or other wireless communications network capable of sending and receiving telephone calls. Further, wireless communication device  53  is capable of communicating via the Internet to access email, download content, access websites, and provide steaming audio and/or video programming. In this fashion, wireless communication device  53  can place and receive telephone calls, text messages such as emails, short message service (SMS) messages, pages and other data messages that can include attachments such as documents, audio files, video files, images and other graphics. 
     FIG. 3D  illustrates an embodiment of a personal digital assistant (PDA)  54 . In particular, disk drive unit  100  can be implemented in the personal digital assistant (PDA)  54 . In one possible embodiment, disk drive unit  100  can include a small form factor magnetic hard disk whose disk  102  has a diameter 1.8″ or smaller that is incorporated into or otherwise used by personal digital assistant  54  to provide general storage or storage of audio content such as motion picture expert group (MPEG) audio layer  3  (MP3) files or Windows Media Architecture (WMA) files, video content such as MPEG4 files, JPEG (joint photographic expert group) files, bitmap files and files stored in other graphics formats, emails, webpage information and other information downloaded from the Internet, address book information, and/or any other type of information that may be stored in a digital format. 
     FIG. 3E  illustrates an embodiment of a laptop computer  55 . In particular, disk drive unit  100  can be implemented in the laptop computer  55 . In one possible embodiment, disk drive unit  100  can include a small form factor magnetic hard disk whose disk  102  has a diameter 1.8″ or smaller, or a 2.5″ drive. Disk drive  100  is incorporated into or otherwise used by laptop computer  52  to provide general purpose storage for any type of information in digital format. 
   When implementing ECCs within devices that include HDDs, there are typically many different types of processes that are performed during the decoding processing. Various types of ECCs can be employed including turbo coding, turbo trellis coded modulation (TTCM), parallel concatenated turbo code modulation (PC-TCM), Reed-Solomon (RS) coding, LDPC (Low Density Parity Check) coding, and/or other types of ECC. 
   For each of these particular types of codes, certain of these processes are more computationally intensive and require more clock cycles than others. Various aspects of the invention provide for an efficient allocation of the clock cycles, real estate, and/or overall processing capabilities of the device to provide for an overall high performance of the ECC decoding processing. 
   Considering one particular type of ECC, namely, RS coding, when RS ECC blocks with a hardware on-the-fly ECC system, a substantial amount of the allotted ECC correction time budget seems to be is dedicated to performing one particular function within the RS decoding processing. Perhaps the most consumptive function, in terms of the allotted ECC correction time budget, is the Chien Search operation. Looking perhaps more specifically, because a substantial portion of the ECC correction time budget is spent on performing the Chien Search function, the processing of the remaining functions within the of the RS decoding processing are squeezed into a small portion of the allotted time. This can result in excessive parallelism in the design making an on-the-fly ECC correction system consume extensive amounts of area and power. Alternately, this problem may result in an ECC architecture with additional pipeline latency. Moreover, the instantaneous power consumption may not be optimal. 
   In a typical implementation, one clock cycle is required per symbol of the block size. However, the Chien Search operation typically requires a minimal amount of register-to-register logic for the resulting synthesized hardware. One approach and embodiment by which efficiency can be achieved is to use multiple frequencies of the same clock signal. For example, a first clock signal can be employed to clock the Chien Search operation, and a second clock signal can be employed to clock at least one additional function within the RS decoding processing. Alternatively, this second clock signal can be employed to clock all of the remaining functions within the RS decoding processing except the Chien Search operation. In one particular embodiment, a higher rate clock signal can be employed to clock the Chien Search operation, and a lower rate clock signal can be employed to clock at least one additional function (or all of the remaining functions) within the RS decoding processing. 
   To ensure appropriate synchronization between these two clock signals, they can be implemented within a common clock tree network. This will help ensure that the skew of the clock signals are aligned and balanced properly. This can be achieved using clock tree synthesis modules, as is described in some of the later embodiments as well. By operating at least one function of the RS decoding processing according to one clock signal, and at least one other function (or all of the remaining functions) of the RS decoding processing according to another clock signal, the overall ECC correction time is significantly reduced. This can provide for numerous performance gains including an overall area and power reduction of the whole ECC system by providing more clocks for the remaining functions and/or reducing the number of sector pipeline stages required to perform a correction. 
   If desired, certain properties of the other clock signal (e.g., the second clock signal) can be dynamically modified in real time based on certain parameters. For example, the frequency of the clock signal that is used to run the Chien search function can be selected based on the amount of time remaining to complete the ECC decoding processing within the allotted ECC correction time. For example, the frequency of that clock signal can be modified, in real time, based on how close (or how far) the overall decoding processing is from the total allowed and dedicated time. Alternatively, the frequency of the clock signal that is used to run the Chien search function can be selected based on the number of errors that is identified within the particular ECC decoding processing being employed. For example, when looking at the total number of errors identified within RS decoding processing, then the frequency of the clock can be adjusted accordingly. By adjusting the frequency of the clock in response to such a parameter, the instantaneous power consumption of the device can be smoothed as well thereby providing for improved performance. 
     FIG. 4  illustrates an embodiment of an apparatus  400  that includes a Reed-Solomon (RS) decoder employing two different clock signals. A 1 st  clock signal  401  is provided to a clock frequency processing module  420 . The clock frequency processing module  420  can be a divider, a multiplier, a combination thereof, and/or a module that is operable to perform any desired processing of the 1 st  clock signal  401  to generate a 2 nd  clock signal  402 . Both the 1 st  clock signal  401  and the 2 nd  clock signal  402  are provided to a RS decoder  410  that is operable to perform error correction decoding processing (i.e., RS decoding processing) on data  405 . Oftentimes, the data  405  are partitioned into blocks of data (e.g., ECC blocks) before or as they are received by the RS decoder  410 . A 1 st  processing module  412  within the RS decoder  410  receives the 1 st  clock signal  401 , and a 2 nd  and/or other processing module(s)  414  within the RS decoder  410  receive/receives the 2 nd  clock signal  402 . For example, the 2 nd  and/or other processing module(s)  414  can include as few as 1 processing module or as many as all of the remaining processing modules of the RS decoder  410  except the 1 st  processing module  412 . It is noted that although separate and distinct processing modules are depicted herein, a software and/or digital equivalent of each of these processing modules can be implemented such that each processing module corresponds to a function and/or functions that is/are performed within the RS decoding processing as well without departing from the scope and spirit of the invention. 
   If desired, one or more feedback signals  411  can be provided to the clock frequency processing module  420  from the RS decoder  410  to govern at least one parameter of the 2 nd  clock signal  402 . For example, the frequency, skew, or other parameter of the 2 nd  clock signal  402  can be adjusted in response to the one or more feedback signals  411 . 
   The RS decoder then operates the 1 st  processing module  412  according to the 1 st  clock signal  401 , and the 2 nd  processing module  414  according to the 2 nd  clock signal  402  when performing RS decoding processing thereby generating error corrected data  415  from the data  405 . This error corrected data includes best estimates of the information that was originally encoded using corresponding RS encoding processing. Analogously to how the data  405  are sometimes partitioned into blocks of data (e.g. ECC blocks), the error corrected data  415  can also be provided from the RS decoder  410  as blocks of error corrected data as well. 
     FIG. 5  illustrates an alternative embodiment of an apparatus  500  that includes a RS decoder employing two different clock signals. A 1 st  clock signal  501  is provided to a clock frequency processing module  520 . The clock frequency processing module  520  can be a divider, a multiplier, a combination thereof, and/or a module that is operable to perform any desired processing of the 1 st  clock signal  501  to generate a 2 nd  clock signal  502 . It is noted that the clock frequency processing module  520  can be implemented in a clock tree network  530  such that each of the 1 st  clock signal  501  and the 2 nd  clock signal  502  are contained within the same clock tree network  530 . By implementing each of these clock signals in a common clock tree network, the skew of each of the 1 st  clock signal  501  and the 2 nd  clock signal  502  will be aligned and balanced well. 
   Both the 1 st  clock signal  501  and the 2 nd  clock signal  502  (generated within a common clock tree network in some embodiments) are provided to a RS decoder  510  that is operable to perform error correction decoding processing (i.e., RS decoding processing) on data  505  that is received from a storage media  590 . More specifically, the data  505  is typically retrieved via a channel  595  of the storage media  590 . As mentioned within at least one other embodiment, the data  505  can be partitioned into blocks of data (e.g., ECC blocks) before or as they are received by the RS decoder  510 . A Chien search module  512  within the RS decoder  510  receives the 1 st  clock signal  501 , and one or more other processing module(s)  514  within the RS decoder  510  receive/receives the 2 nd  clock signal  502 . For example, the one or more other processing module(s)  514  can include as few as 1 processing module or as many as all of the remaining processing modules of the RS decoder  510  except the 1 st  processing module  412 . As within other embodiments, it is noted that although separate and distinct processing modules are depicted herein, a software and/or digital equivalent of each of these processing modules can be implemented such that each processing module corresponds to a function and/or functions that is/are performed within the RS decoding processing as well without departing from the scope and spirit of the invention. 
   If desired, one or more feedback signals  511  can be provided to the clock frequency processing module  520  from the RS decoder  510  to govern at least one parameter of the 2 nd  clock signal  502 . For example, the frequency, skew, or other parameter of the 2 nd  clock signal  502  can be adjusted in response to the one or more feedback signals  511 . 
   The RS decoder then operates the Chien search module  512  according to the 1 st  clock signal  501 , and the one or more other processing module(s)  514  according to the 2 nd  clock signal  502  when performing RS decoding processing thereby generating error corrected data  515  from the data  505 . This error corrected data includes best estimates of the information that was originally encoded using corresponding RS encoding processing. Analogously to how the data  505  are sometimes partitioned into blocks of data (e.g. ECC blocks), the error corrected data  515  can also be provided from the RS decoder  510  as blocks of error corrected data as well. 
   In some embodiments, it is noted that the 2 nd  clock signal  502  is an integer multiple of the 1 st  clock signal  501 . For example, the 2 nd  clock signal  502  can have a frequency that is twice the frequency of the 1 st  clock signal  501  in some embodiments. If desired, the 2 nd  clock signal  502  can be a frequency up converted version of the 1 st  clock signal  501 . Alternatively, the Chien search module  512  and the one or more other processing module(s)  514  can be switched in the RS decoder  510  such that the Chien search module  512  operates according to the 1 st  clock signal  501 , and the one or more other processing module(s)  514  operates according to the 2 nd  clock signal  502 . 
   In such an embodiment, when desired to operate the Chien search module  512  at a higher frequency than the one or more other processing module(s)  514 , the clock frequency processing module  520  could be implemented as a divider, such that the 1 st  clock signal  501  (which is provided to the one or more other processing module(s)  514  in such an alternative embodiment) is an integer multiple of the 2 nd  clock signal  502 . 
   Clearly, a wide variety of permutations can be implemented such that the Chien search module  512  operates according to a 2 nd  clock signal  502 , and the one or more other processing module(s)  514  operates according to a 1 st  clock signal  501 . In some instances, the 2 nd  clock signal  502  is an integer multiple of the 1 st  clock signal  501 . 
     FIG. 6  illustrates an embodiment of an apparatus  600  that employs two clock tree synthesis modules. This embodiment shows a 1 st  clock signal  601  that is provided to a clock frequency processing module  620 . The clock frequency processing module  620  can be a divider, a multiplier, a combination thereof, and/or a module that is operable to perform any desired processing of the 1 st  clock signal  601  to generate a 2 nd  clock signal  602 . 
   The 2 nd  clock signal  602  is provided to a clock tree synthesis module  631 , and t he 1 st  clock signal  601  is provided to a clock tree synthesis module  632 . The use of the clock tree synthesis module  631  and the clock tree synthesis module  632 , which can implemented within a common clock tree network (if desired), allows for the skew of the 1 st  clock signal  601  and the 2 nd  clock signal  602  to be aligned and balanced properly. 
   Subsequently, when each of the 1 st  clock signal  601  and the 2 nd  clock signal  602  is provided to the subsequent circuitry (e.g., flops as depicted using reference numeral  641 ), the skew of these signals are aligned properly such that the signals generated within each of the clock tree synthesis module  631  and clock tree synthesis module  632  have the rise times that correspond (at shown at least on the transitions that align as a function of the integral multiple difference in frequency between the two signals). In this embodiment, the clock signals generated by the clock tree synthesis module  632  from the 1 st  clock signal  601  are shown as having a frequency that is one half the frequency of the clock signals generated by the clock tree synthesis module  631  from the 2 nd  clock signal  602 . Clearly, as desired in a particular application, any integral multiple of frequency may be employed as being the difference between the 1 st  clock signal  601  and the 2 nd  clock signal  602 . 
     FIG. 7  illustrates an embodiment of a RS decoder  700  that performs at least Chien searching. This is a general depiction of an architecture of a RS decoder  700 , and it is noted that variations and/or modifications thereof may be performed without departing from the scope and spirit of the invention. At a minimum, the RS decoder includes an error location search module  730  (that can be implemented by performing Chien searching, as depicted using reference numeral  732 ). 
   A corresponding RS encoder (not shown) takes data (e.g., a block of digital data) and adds redundancy or parity bits thereto thereby generating a codeword (e.g., a codeword to be written or transmitted). This redundancy is generated as a function of the particular RS code employed. Therefore, when the data (after undergoing RS encoding) is provided to storage media, and after it is read there from, in the undesirable event that any errors occurred during either of these processes (write and/or read), hopefully the number of errors incurred is less than the error correcting capability of the RS code. The number and types of errors that can be corrected depends on the particular characteristics of the RS code employed. 
   Looking at  FIG. 7 , a received codeword  791  can be viewed as being the originally transmitted (or written) codeword plus any errors that have been incurred during the write and/or read processes to the media. In addition, perhaps some defects occurred to the actual physical surface of the storage media after the codeword has been written. This received codeword would then also include those incurred errors as well. Generally speaking, the RS decoder  700  attempts to identify the locations and magnitudes of any errors within the received codeword  791  (up to the error correcting capability of the RS code) and to correct those errors. 
   A syndrome calculation module  710  then processes the received codeword  791  to generate syndromes  792 . The operation of the syndrome calculation module  710  is analogous and similar to the calculation of the redundancy or parity bits within the RS encoding processing. As a function of the RS code employed, a RS codeword has a predetermined number of syndromes that depend only on errors (i.e., not on the actually written or transmitted codeword). The syndromes can be calculated by substituting a predetermined number of roots (as determined by the RS code) of the generator polynomial (employed within RS encoding) into the received codeword  791 . 
   An error locator polynomial generation module  720  then receives these calculated syndromes  792 . The syndromes  792  are also passed to an error magnitude calculation module  740  (more detail of which is provided below). The error locator polynomial generation module  720  can generate the error locator polynomial  793  using various means, two of which can include the Berlekamp-Massey method  722  or Euclid method  724 , as known in the art. 
   The error locator polynomial  793  is provided to an error correction module  750 . The error locator polynomial  793  is also provided to an error location search module  730  that is operable to solve for the roots of the error locator polynomial  793 . One approach is to employ the Chien search function  732 . Within the overall RS decoding processing, a substantial portion of the RS decoding processing time budget is spent on performing the Chien search function  732 , the processing of the remaining functions within the of the RS decoding processing are squeezed into a small portion of the allotted time. 
   Once the error locations  794  have been found within the error location search module  730  (i.e., using the Chien search function  732 ), then the error locations  794  are provided to the error magnitude calculation module  740  as well as to the error correction module  750 . The error magnitude calculation module  740  finds the symbol error values, and it can employ a known approach such as the Forney method  742 . Once the error locations  794  and the error magnitudes  795  are known, then the error correction module  750  corrects for them and outputs an estimated codeword  796 . 
   Looking at this embodiment, many of the modules and/or functions within the RS decoder  700  operate using a 1 st  clock signal  701 , and the error location search module, in particular the Chien search function  732  located therein, operate using a 2 nd  clock signal  702 . In some instances, the 2 nd  clock signal  702  employing by the error location search module, particularly by the Chien search function  732  located therein, is an integer multiple of the 1 st  clock signal  701 . 
   Generally speaking, it can be seen that the clock signal employed by the error location search module, particularly by the Chien search function  732  located therein, is different from the clock signal employed by at least one (and/or all of the other) modules within the RS decoder  700 . 
     FIG. 8  illustrates an embodiment of a method  800  that performs RS decoding. The method  800  operates by receiving a first clock signal having a first frequency as shown in a block  810 . The method  800  then operates by generating a second clock signal having a second frequency using the first clock as shown in a block  820 . As shown in a block  830 , the method  800  continues by performing Reed-Solomon (RS) error correction decoding on data that includes performing Chien searching to search for a location of an error within the data and that includes at least one additional RS decoding function. 
   The method  800  also involves performing the at least one additional RS decoding function according to the first frequency of the first clock as shown in a block  840 , and the method  800  also involves performing the Chien searching according to the second frequency of the second clock as shown in a block  850 . In some embodiments, the second frequency is an integer multiple of the first frequency, as shown in a block  852 . 
   In view of the above detailed description of the invention and associated drawings, other modifications and variations will now become apparent. It should also be apparent that such other modifications and variations may be effected without departing from the spirit and scope of the invention.

Technology Category: 5