AN3324

How to implement power-on self test features

Doc ID 18311 Rev 2

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How to implement power-on self test features

The goal of this application note is to show how users can implement properly the safety

2.1

MCU initialization

At power-on, after register initialization (see Section 3.3: Redundancy Control Checker Unit

(RCCU)) and other basic initializations (MMU configuration, stack initialization, etc.) (see

Appendix A: CPU core initialization) user software has to verify if MCU is in alarm state or in

safe mode (coming from a Reset Condition) (see Section B.1: Reference documents in

Appendix B) and in that case must manage fault causes.

If current mode in Mode Entry module is default run mode (DRUN), software can proceed

with the default safety MCU initialization with self test features (see Figure 1: Initialization

flow).

Note:

User can verify alarm state by reading Non Critical Fault on FCCU while he can verify safe

mode by reading Current Mode field (GS register) on Mode Entry module.

a.

Latent fault: multiple point fault whose presence is not detected by a safety mechanism nor perceived by the

driver within the multiple point fault detection interval.