SPRUIZ1B July 2023 – August 2024 TMS320F28P650DH , TMS320F28P650DK , TMS320F28P650SH , TMS320F28P650SK , TMS320F28P659DH-Q1 , TMS320F28P659DK-Q1 , TMS320F28P659SH-Q1
ROMs are read-only memory, unlike RAMs, data or parity bits cannot be modified to introduce errors for diagnostic coverage of parity checking logic. The following method is used to check health of parity checking logic in ROMs.
The probability of both circuits having fault is unlikely; hence, Parity Errors are certainly detected.
To generate the error, a test bit FORCE_ERROR is added. When the FORCE_ERROR bit is set, the parity bit going to one of the party checkers is inverted; thereby, introducing an uncorrectable error. An uncorrectable error is generated only if there is an error on all parity checkers: address, data [15:0], and data [31:16]. This makes sure that all three parity checkers are working as expected. See Figure 3-19.
Figure 3-19 ROM Parity Checking
Logic