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MSP432P401R: Issues with instructions skipping or jumping to the wrong address

David Bartholome
Prodigy 20 points

Part Number: MSP432P401R

I designed a board using the MSP432P401R and am seeing some issues on a couple of them. While performing a test one of my boards skipped a series of instructions and jumped to the end of the test. This issue was not repeatable on that board and it has been through extensive testing before seeing this issue. 

A different board exhibited somewhat similar behavior, but it jumped to the same incorrect address several times in a row. This problem seemed to have cleared by cycling power on the device as we have not been able to reproduce it since.

Going through some of the documentation it looks like I missed including a capacitor on the Vcore pin. At first that seemed to be the most likely problem, but would I see this failure so rarely if that were the case? 

We've run the debugger while stepping through the test sequence and saw no issues on the memory browser, so it doesn't seem to be a SW problem. 

The boards have been coated so probing the Vcore pin would not be an easy task at this point. 

Any recommendations on what we could check to narrow down the potential issues, or is this more likely to be a problem with another part of the board?

If the problem is the missing capacitor, would increasing core voltage to 1.4V instead of the 1.2V we're using (running at 24MHz) be a potential fix?

Thanks,

David 

  • 0
    Prodigy 120 points

    Hi David, I'm not an expert myself so please be careful with the following statement, however the VCORE - Pin definitively needs the external capacitor to stabilize the VCORE voltage. If not available this might result in the undefined behavior you're experiencing. Therefore I would try to remove the coating carefully to access the VCORE pin and add the external capacitor. MAYBE this stabilizes the behavior.

    All the best
    Aaron 

  • 0
    TI__Guru 56685 points

    David,

    I have to agree with Aaron here. Without the recommend capacitor value on VCORE pin, you are operating the device out of specification. Its execution could be unpredictable and correct operation cannot be guaranteed. I'm surprised you got the chip behaving properly at all without this component.

  • 0 in reply to Aaron Hillinger
    Prodigy 20 points

    Aaron/Jace,

    Thanks for the feedback. The missing capacitor seems like the issue, the only reason I've been hesitant about adding it at this point is because I have not been able to repeat this behavior on my boards. Are there additional factors that help stabilize the core voltage which results in fewer issues? I'm just trying to understand why this is happening very rarely as I've tested through several iterations of the board without seeing this type of problem. 

    They way you describe it, it sounds like this would've been obvious from the beginning and I would be having this issue much more frequently.

    Thanks,

    David 

  • +1 in reply to David Bartholome
    TI__Guru 56685 points

    Hey David,

    Without that capacitor keeping VCORE stable, all bets are off. You could possibly have an additional issue, but it won't be apparent if you do or not until this first one is addressed. It could be that the inherent capacitance of the board stack up is helping you here, or just that the pin is floating in just the right way. If you would have grounded the pin, the part wouldn't of started up at all I imagine. Not sure though as that's not a scenario that's tested. 

  • 0 in reply to Jace H
    Prodigy 20 points

    Hey Jace,

    Thanks for the info, I'll start with the capacitor.

    David