problem between FS85 and S32k in programming process

[Luis_HW_26]

Hi all,

I've designed a board with a uC s32k and a FS8510A SBC to get safety characteristics. The idea is to power supply the SBC with external 12V and use the output LDO2 (5V) of the SBC to power supply the uC. Also, I have the option to power up the microcontroller externally with 5V.

When I power supply the uC externally, I don't have any problem for programming it and after that, connect the uC to the SBC for configuring the WDG and OPT options using SPI communication. all works correctly.

However, if I power supply from the SBC and I try to program a new code in the microcontroller, the SBC cut off the output voltage and the uC is bricked. I think this problem ocurrs because the WDG is not present during the programming process and the SBC doesn't detect it. I've tried to enter the SBC in debug mode with the aim to avoid the restart of the SBC for the WDG, but in debug mode, the SBC cuts off the LDO output also.

So, my question is: Are there any option for the SBC maintain the LDO output during the debug mode in order to power supply from the SBC in the programming process and not need an external power supply for the uC.

Thanks in Advance!!

[RafaR]

Hello Luis_HW_26

Good day!

No, unfortunately the FS85 cannot keep the LDO output active during debugging.

But to perform your test, you can disable watchdogs in the INIT_FS phase.

Here's an example a colleague did in the past:

https://community.nxp.com/t5/Power-Management/Disable-FS85-watchdog-in-normal-mode-for-in-vehicle-pr...

I hope this information has helped you, please let me know if you need help with anything else.

Have a great day and best of luck.