Theory
Data Integrity
41
C2 ECC
C2 ECC involves three distinct operations:
1.
Encoding
: Generating C2 ECC bytes from data bytes (performed by ECC co-processor hard-
ware)
2.
Decoding
: Generating ECC syndromes from data and ECC bytes, testing for all-zeroes (per-
formed by ECC co-processor hardware)
3.
Correction
: Generating corrected data from syndromes.
The correction depends on the number and types of errors involved:
•
For one known C1 codeword pair in error in a sub-data set (C2 codeword), the operation is
performed by the ECC co-processor hardware.
•
For two or more known C1 codeword pairs in error, the matrix is computed by firmware and
the correction is performed by hardware.
•
For one or more unknown C1 codeword pairs, syndromes are generated by hardware, error
location is computed by firmware, the matrix is computed by firmware and the correction is
performed by hardware.
Servo-tracking Faults
During a write operation, if the servo system detects an error that may result in adjacent data tracks
being over-written, the write operation is aborted. The write operation will not continue until the cor-
rect servo tracking is re-established.
