The device can permanently disable the battery pack in the case of a severe failure, such as an error in the instruction flash check (IFC) or in the data flash write (DFW). An IFC failure is set by the gauge if the signature fails to pass verification at power-on reset. The DFW failure is set by the gauge if it is unable to successfully program an update to the data flash (the read-back verification fails). When one of these failure modes is detected, the following actions are taken in sequence:
- Charge and discharge FETs are turned off.
- OperationStatus()[PF] = 1
- The following data is changed: BatteryStatus()[TCA] = 1, BatteryStatus()[TDA] = 1, ChargingCurrent() = 0, and ChargingVoltage() = 0.
- A backup of the internal AFE hardware registers are written to data flash: AFE Interrupt Status, AFE FET Status, AFE RXIN, AFE Latch Status, AFE Interrupt Enable, AFE FET Control, AFE RXIEN, AFE Cell Balance, AFE AD/CC Control, AFE ADC Mux, AFE State Control, Wake Control, AFE Protection Control, AFE OCD, AFE SCC, AFE SCD1, and AFE SCD2.
- The following values are preserved in data flash for failure analysis:
- SafetyAlert()
- SafetyStatus()
- OperationStatus()
- ChargingStatus()
- GaugingStatus()
- Voltages in DAStatus1()
- Current()
- TSINT, TS1, from DAStatus2()
- Cell DOD0 and passed charge
- Data flash writing is disabled.
While the device is in this PERMANENT FAIL mode, any new SafetyAlert(), SafetyStatus() flags that are set are added to the permanent fail log.