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Hot!MCLR pin not resets the PIC32MZ

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2020/08/06 10:57:02 (permalink)

MCLR pin not resets the PIC32MZ

Hi all,
I have a problem with pic32mz0512eff144. I have a custom desgined board by me which I programmed numerous times before. Suddenly it stopped programming. I see "failed to get device ID" error while programming. I have ICD3 and ICD4 and both give same error message. Device keeps running with last programmed code I can not program new one. So I decided to control MCLR signals.
I use attached reference design from PIC32 MZ datasheet (DS60001320G) with single change. I only added a tact reset switch parallel to cap C. When I pressed the reset switch, I see 0V on MCLR pin but very very strangely PIC keeps running the last program on its memory. I see 0V on MCLR line, but I can not reset the device. Do you have an idea about what is happennig?

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    Re: MCLR pin not resets the PIC32MZ 2020/08/06 12:59:43 (permalink)
    Are you sure that /MCLR signal is measured at the correct point? At the pin, not the switch?
    As long as PICkit programming/ debugging tool is connected,
    PICkit will drive /MCLR pin high, and override reset switch.
    Resistor R1 = 1kOhm providing signal isolation.
    You may try experiment with programming tool disconnected.
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    Re: MCLR pin not resets the PIC32MZ 2020/08/06 14:15:06 (permalink)
    Assuming you're measuring correctly, either some soldering fell apart, or the PIC got damaged.
    Do you have projects for PIC16/PIC18? If so, you might have tried to program one of such projects while your PIC32 board was connected. This applies 9V or even 13V to MCLR. This is a sure kill for PIC32's MCLR pin.
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