WKSF - WAK bit FAILSAFE of TLF35884

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User22192
Level 2
Level 2
10 sign-ins First solution authored First like received

Hello,

I have following situation. I force the TLF35584 chip into FAILSAFE by 3 consecutive init timer violation, during this entire time the WAK bit of the chip is supplied by a constant "high" voltage.

The observed behavior is that the HW goes to FAILSAFE and immediately recover, still I can not see afterwards the WKSF.WAK bit set as the cause of exiting the FAILSAFE.

Any help, please? Thanks

PS: auto-recovery from FAILSAFE is prevented by forcing TLF in FAILSAFE 3 times before doing the test above.  

 

 

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1 Solution
Albab_A
Moderator
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5 likes given 50 solutions authored 100 replies posted

Hello,

I have one follow-up question for you.

Did did you checked whether WKSF bit was set or not before the three failure events on reaching FAILSAFE or after those three events?

Moreover, in your situation, it's possible that the constant "high" voltage on the WAK pin is causing the TLF35584 chip to exit Failsafe mode prematurely, without triggering a WAK event. The WAK pin is used to detect external events that can trigger the exit from Failsafe mode, and a constant high voltage on this pin can mask any potential external events that may have triggered the exit.

One way to verify if this is the case is to temporarily disconnect the constant high voltage source from the WAK pin and allow the chip to enter Failsafe mode again. If the WKSF.WAK bit is set after a Failsafe event, this would indicate that the constant high voltage source is causing the issue.

Best Regards,

Albab

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4 Replies
AnilKumar
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First question asked 50 solutions authored 10 likes received

Hello,

FAILSAFE to INIT state is a self-triggered event with Timer getting expired (minimum FAILSAFE time
tFAILSAFE,min,20 ms for all failures except a thermal shutdown) and doesn't require an EN or Wake.
EN or Wake is required only when failsafe is entered 3 times in a row with the same failure (as mentioned in datasheet 11.3.8, Exceptions).

Please ensure if all 3 were same failures and consecutively in a row to fall under exceptions (i.e. an EN/WAK is required to wake-up the device) as explained above.

Please share IF and WKSF register values.

Thanks

Anil

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Hi, thanks for the reply!

The code looks like this:

TLF is in NORMAL state => trigger a MoveToInit  e.g. while(1) -> "wwdog reset"

During initialization: (TLF is in INIT)

if (SYSFAIL != 0) {//SYSFAIL = 128(INTF flag set)

            if ((WKSF.WAK == 1) || (WKSF.ENA == 1)) {//FailsafeRecovery}

            else {while(1);  // Force init timeout }

} else {while(1); // Here in can be seen INITERR with its different values}

 

My issue: if HIGH level is applied to the WAK pin from the begining before making the first MoveToInit transition , it will never reach "FailsafeRecovery branch" as the WAK bit is not set into the WKSF. Maybe an additional question: in which condition the Failsafe SelfTrigger Recover Counter is reset?

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Albab_A
Moderator
Moderator
Moderator
5 likes given 50 solutions authored 100 replies posted

Hello,

I have one follow-up question for you.

Did did you checked whether WKSF bit was set or not before the three failure events on reaching FAILSAFE or after those three events?

Moreover, in your situation, it's possible that the constant "high" voltage on the WAK pin is causing the TLF35584 chip to exit Failsafe mode prematurely, without triggering a WAK event. The WAK pin is used to detect external events that can trigger the exit from Failsafe mode, and a constant high voltage on this pin can mask any potential external events that may have triggered the exit.

One way to verify if this is the case is to temporarily disconnect the constant high voltage source from the WAK pin and allow the chip to enter Failsafe mode again. If the WKSF.WAK bit is set after a Failsafe event, this would indicate that the constant high voltage source is causing the issue.

Best Regards,

Albab

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Hello and thanks for the reply.

I can confirm the last statement, that if I let the chip enter FAILSAFE and only afterwards apply a HIGH on WAK then I can see WKSF.WAK bit set, but I would expected to be set also in my test case, or at least to have a confirmation that the FAILSAFE was exited due to WAK HIGH even if it was set before entering FAILSAFE.

Best regards!

Thanks. 

 

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