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Section 25 NAND Flash Memory Controller
R01UH0134EJ0400 Rev. 4.00 Page 1333 of 2108
Sep 24, 2014
SH7262 Group, SH7264 Group
(1) Overview of 4-Symbol ECC Circuit
The 4-symbol ECC circuit in this module is capable of correcting up to 10 bits per symbol, which
makes a maximum of 40 bits for four symbols. However, the circuit corrects up to 32 bits because
the data in the flash memory data area is counted as eight bits per symbol.
Error correction pattern generation means generation of information necessary for correcting
errors, not execution of error correction. For details, see section 25.4.6, (3) 4-Symbol ECC Error
Correction Pattern Generation.
The 4-symbol ECC circuit is roughly divided into three stages (figure 25.15).
1. ECC generator
2. Error count detector
3. Error correction pattern generator
ECC generation and error count detection can be executed continuously while error correction
pattern generation is executed on a sector-by-sector basis.
Register
Flash memory
External memory
4-symbol ECC
error count
detector
4-symbol ECC circuit
This module
512 bytes (data)
+
10 bytes (ECC)
4-symbol ECC
generator
4-symbol ECC
error correction
pattern
generator
4-symbol ECC processing result 1
4-symbol ECC processing result 2
4-symbol ECC processing result 3
4-symbol ECC processing result 4
ECC error count register
Register
Figure 25.15 4-Symbol ECC Circuit