New DEVKIT-S12ZCV Fails to boot

[nateimig]

Hello,

Our group observed an issue with the DEVKIT-S12ZCV not reliably booting up on power up approximately 15-30% of the time. We have isolated it down from something we could be doing wrong in software, to using a brand new DEVKIT-S12ZCV still w/ the default demo program cycling the RGB color.

We have found that when a debug USB micro is attached to a PC/Laptop and the DEVKIT-S12ZCV this issue completely disappears and reliably starts up every time, even though the USB does not power the target board.

Here is a video/demonstration of the issue:

https://youtu.be/bUyQUZc91YQ

Theres a similar post here but may not be related:

https://community.nxp.com/t5/S12-MagniV-Microcontrollers/S12Z-fails-to-boot/m-p/1223558

Any help or suggestions to narrow down/fix this issue would be greatly appreciated!
Thanks

[nateimig]

So to update whomever sees this, the remedy or fix seems to be isolated to some unwanted power off behavior in the MCU-OSBDM voltage
translators isolated to U3 after removing/cutting away SH7 from connecting TBGND and BKGD the unreliable booting goes away however now the target can't be flashed by the OSBDM Interface...

 

[nateimig]

So a better solution recently found is to populate the DNP pullup resistor to VDDX (R7) also connected to the BKGD signal. Not sure why this was remove or not populated but its 100% fixed and reliably booting up with this tweak and even better the OSBDM interface still can flash and debug...

Does anybody potentially know of a hardware fuse like bit to fix this issue or a permanent disable of this MODC pin causing to go into Special Single-Chip Mode from the dual functionality pin (BKGD/MODC) that seems to cause a boot up failure?

Bueller

[lama]

Hi,

Hmmm, this was standard recommendation in past to pull the MODC up with external 4.7K resistor because the internal one is too weak. I appreciate your approach to solution. I was solving the issue with   colleagues of mine but this fact we absolutely forgotten because the issue related to it has not appeared for a long time.

Your dynamical switching on and off can cause something which enters MCU into a debug mode (MODC=0) so it is not running. Pull up resistor improves environment for such switching and enters the MCU in normal mode without issues caused by transient states.

Best regards,

Ladislav

[nateimig]

Hey Ladislav, 

Thank you for the reply/confirmation.