What Happens when you dont close the INIT_FS Phase before the 256ms timeout on the FS26 watchdog

[MFaheem]

Need help answering these question: 

1- in what state does the FS26 end up into if I don't close the INIT_FS phase with 1 good watchdog refresh within the preconfigured 256ms timeout ? 

2- Is the INIT_FS phase timeout configurable ? what's exactly happening with "WD_INIT_TIMEOUT_OTP" is it deprecated or not usable or planned for future use ?

3- Does the WD_DIS OTP bit Enables/Disables watchdog completely or just the timeout for the INIT_FS phase ? 

4- From functional Safety POV, normally in Autosar projects when doing a transition between Application and Bootloader you issue an MCU reset, which asserts the release line and the FS26 will react by going back to INIT_FS phase, this mean the WDG can be ineffective for 256ms ... is that the intentional design ? any hints for how this should work "handling the FS26 WDG when transitioning from application to bootloader" ? 

[diazmarin09 · Accepted solution]

Hello Mohammed,

I hope all is great with you.

Please review the information below:

1. Device will reset every 256ms and stay in INIT_FS mode.
2. WD_INIT_TIMEOUT_OTP can configure the INIT_FS timeout period, but it leave 256ms by default and did not open to customer for configuration. Do you have use case that must change the INIT_PHASE period ?
3. WD_DIS OTP will disable watchdog completely.
4. For FS26, there is a SPI Command "Go_INIT" and RSTB is always high, this mean the WDG can be ineffective for 256ms.

So it can be used to re-configure FS26 WDG and disable FCCU when transitioning from application to bootloader.

Regards,

David

[MFaheem]

Thanks alot for the reply  

1- Ok

2- No, I was just exploring the possibility to disable that timer to make it more strict

3- Ok 

4- My assumption was that the Wdg should be expecting good refreshes even when doing a transition between APPL and Boot, but i think the current setup makes it a bit more relaxed way of handling the Wdg