Preliminary
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Error Location Module
1.15 Error Location Module
1.15.1 Error Location Module Overview
Non-managed NAND flash memories can be dense and nonvolatile in their own nature, but error-prone.
When reading from NAND flash memories, some level of error-correction is required. In the case of NAND
modules with no internal correction capability, sometimes referred to as bare NANDs, the correction
process is delegated to the memory controller.
The general-purpose memory controller (GPMC) probes data read from an external NAND flash and uses
this to compute checksum-like information, called syndrome polynomials, on a per-block basis. Each
syndrome polynomial gives a status of the read operations for a full block, including 512 bytes of data,
parity bits, and an optional spare-area data field, with a maximum block size of 1023 bytes. Computation
is based on a Bose-ChaudhurI-Hocquenghem (BCH) algorithm. The error-location module (ELM) extracts
error addresses from these syndrome polynomials.
Based on the syndrome polynomial value, the ELM can detect errors, compute the number of errors, and
give the location of each error bit. The actual data is not required to complete the error-correction
algorithm. Errors can be reported anywhere in the NAND flash block, including in the parity bits.
The maximum acceptable number of errors that can be corrected depends on a programmable
configuration parameter. 4-, 8-, and 16-bit error-correction levels are supported. The ELM relies on a static
and fixed definition of the generator polynomial for each error-correction level that corresponds to the
generator polynomials defined in the GPMC (there are three fixed polynomial for the three correction error
levels). A larger number of errors than the programmed error-correction level may be detected, but the
ELM cannot correct them all. The offending block is then tagged as uncorrectable in the associated
computation exit status register. If the computation is successful, that is, if the number of errors detected
does not exceed the maximum value authorized for the chosen correction capability, the exit status
register contains the information on the number of detected errors.
When the error-location process completes, an interrupt is triggered to inform the central processing unit
(CPU) that its status can be checked. The number of detected errors and their locations in the NAND
block can be retrieved from the module through register accesses.
1.15.1.1 ELM Features
The ELM has the following features:
•
4, 8, and 16 bits per 512-byte block error-location based on BCH algorithms
•
Eight simultaneous processing contexts
•
Page-based and continuous modes
•
Interrupt generation on error-location process completion:
–
When the full page has been processed in page mode
–
For each syndrome polynomial in continuous mode
247
SPRUGX9 – 15 April 2011
Chip Level Resources
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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