In Safety Manual following section, I need to understand why Single bit address ECC errors are flagged as uncorrectable errors? I understand that double bit address ECC errorrs are uncorrectable but why single bit ECC errors are uncorrectable?
6.4.3.4 Flash ECC
The on-chip flash memory is supported by single error correction, double error detection (SECDED) error
correcting code (ECC) diagnostic. In this SECDED scheme, an 8-bit code word is used to store the ECC of 64
bit data and corresponding address. The ECC decoding logic at the flash bank output checks the correctness of
memory content. ECC evaluation is done on every data and program read. The data and program interconnects
that connect the CPU and flash memory is not protected by ECC. Detected correctable errors can be corrected
or not corrected, depending on whether correction functionality is enabled. Single bit address ECC errors are
flagged as uncorrectable errors. Errors that cannot be corrected will generate an NMI and ERRORSTS pin is
asserted. Count of the corrected errors (single bit data errors) is monitored in the memory error registers and an
interrupt is generated once the count exceeds the programmed threshold. The corrupted memory address of the
last error location is also logged in the memory error registers.
