[FS45] Question about fault detection and DFS.

[Joey_van_Hummel]

Hi,

I was hoping someone can verify/clarify some passages from the datasheet (Rev. 7).

Passage

12.3: When DFS enabled, the FS state machine monitors and counts faults happening.

Question

1. If DFS is disabled, does the FS state machine not monitor and count faults happening? FLT_ERR_CNT never increments?
2. In that case, is it correct to assume that the intermediate value impact will never trigger?

Passage

12.5.3: The fault error counter is incremented by 1, each time RSTB and/or FS0B pin is asserted. When FS0B is asserted, the fault error counter is incremented by 1, every time the watchdog error counter maximum value is reached.

Question

1. If RSTB and/or FS0B is asserted through SPI request, does it still count towards FLT_ERR_CNT, or only when RSTB/FS0B is asserted as part of a fault impact?
2. If a fault occurs (e.g. VCORE undervoltage) but is configured to have no impact on FS0B or RSTB (e.g. VCORE is not safety critical) am I correct to assume it will not increment FLT_ERR_CNT? E.g. the selected impact on safety outputs FS0B and RSTB determines if it will increment the fault counter?
3. Same question but regarding specifically the second half of the passage: If FS0B is not asserted when the watchdog error counter maximum value is reached, it doesn't increment FLT_ERR_CNT? SO also for the watchdog, the impact defines FLT_ERR_CNT behaviour?

Passage

12.7.1.6 and 12.7.2.4: The overvoltage detection switches off the regulator.

Question

Regarding the disabling of the regulator; is it permanently switched off, until the next Wake-up or POR?

I hope I have understood these passages correctly, but I would like to verify.

Kind regards,

Joey

[TomasVaverka · Accepted solution]

Hi Joey,

A1. No, the fail-safe state machine still monitors, counts faults and FLT_ERR_CNT increases as normal, but the deep fail-safe mode is not entered when the fault error counter reaches max value.

A2. No, intermediate will trigger as it configured.

B1. Yes, SPI request will not increase FLT ERR Counter and only fault impact.

B2. Yes, your understanding is correct.

B3. Yes, you are right.

C. Yes.

Best regards,

Tomas

Best regards,

Tomas

[Joey_van_Hummel]

Hi Tomas,


Thanks for the confirmation, it's much appreciated.

Kind regards,
Joey