The BQ76922 device integrates a signature check on the Instruction ROM, which contains internal controller program code. This PF will be checked at initial powerup or device reset. The Instruction ROM PF (IRMF) can be enabled by setting the Settings:Permanent Failure:Enabled PF C[IRMF] and Settings:Manufacturing:Mfg Status Init[PF_EN] configuration bits.

An instruction ROM signature can be calculated on demand by the host sending the IROM_SIG() subcommand. The signature returned by this subcommand can be compared to the expected value by the host processor, if periodic checks are required. Note that the calculation of this signature takes approximately 9ms, during which time the device will temporarily suspend ADC and coulomb counter measurements and will not respond to serial communications. The device only asserts the IRMF Permanent Fail when the signature check is performed at powerup or reset, it will not assert this if an incorrect signature is returned from the host manually sending the IROM_SIG() subcommand.