Malfunction in entering/waking-up from VLLS states

[gauravbanyal]

Hello,

I am programming an MKL03Z usingn Keil MDK5 and using the J-link probe for flashing and debugging.

I have the following problem. At times, when entering into from run state OR waking-up from VLLS3 or VLLS0 states to RUN states, the system stalls. What I noticed is that the multicolored LED on the Segger J-link plus probe turns Orange and stays there. In the J-link manual, I see the following:

Then I examined the reset line on the oscilloscope and I notice that when this problem happens the reset line looks like this (the BLUE signal which looks like a saw):

The only way to recover from this situation is to flash program the MCU.

The reset pin (PTA1) is connected only to the JTAG port on the reset pin. 

Any ideas on what causes this and how this can be avoided will be a great deal of help.

Best regards,
Gaurav Banyal.

[gauravbanyal]

I just noticed that this problem also happens if I leave the system in VLLS states for some time and have no interaction with the system that might wake the MCU up from the VLLS states.

Please help me urgently.

[jorge_a_vazquez · Accepted solution]

Hi Gaurav Banyal

What is the status of your issue? This reset line is telling that after waking up from VLLSx, the MCU lost the instruction to execute, so it constantly fall in a hard fault, causing a constantly reset in the MCU. Please verify that there isn't any other interrupt source that is preventing your MCU to go correctly to VLLSx.

Also, Please check the followin errata, it could be related with your issue;

5472 SMC: Mode transition VLPR->VLLS0(POR disabled)->RUN, will cause POR & LVD.

Hope this information could help you.

Best Regards

Jorge Alcala

[gauravbanyal]

Hello Jorge,

You are spot on with your suspicion of hitting a hard fault right after a reset. I was able to do some guess work and found the reason for the hard fault. With that fixed, I have never seen the saw-tooth waveform on the reset line again. What remains open still is why it happened only sometimes and not all the times. I will wait for it to happen again and debug it further to a full conclusion on this topic.

Cheers,

Gaurav.