Cold/warm PowerUp Detection without MC_RGM DES/FES registers

[Chris_Cs]

I have a S32K312 (with SCB FS26) software, which should detect a cold/warm powerup. Due to HW layouts, the DES /FES registers cannot be used. Therefore, a memory mapped variable in the standby ram is used, which contains a magic number in case of warm powerups and undefined values in case of cold powerups. To preserve the magic number, this memory area isn’t initialized during startup (otherwise the information would be lost). But a read access on this variable leads to a HardFault.

What is the official nxp way to detect cold/hot powerups, if DES/FES cannot be used?

What needs to be done to handle the hardfault in that way, that there is a safe return to the function, which reads the uninitialized variable, and continue code execution?

[Chris_Cs]

Hello Peter, thank you for reply.

A functional reset of the MCU asserts the RSTB signal, which triggers the circuit outside of the MCU. The circuit then holds the reset for a longer time. Unfortunately this causes a destructive reset and DES=1. That's why DES/FES cannot be used.

Best regards,
Christopher

[petervlna]

Hello,

What is the official nxp way to detect cold/hot powerups, if DES/FES cannot be used?

Official way is always DES/FES. I cannot imagine the situation where these are not available for analyzes.

Can you explain why DES/FES cannot be used? Are the registers inaccessible, cleared before the application can read them, or are you trying to determine something different than the reset source?

Best regards,

Peter