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MCLR/Vpp

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  • MCLR/Vpp

    Unfortunately, I need to use the MCLR/Vpp pin as an input on the 12LF1822.
    Normally I have a pull-up on MCLR. I assume I don't use a pull-up when using the pin as an input and disable MCLR. But what about the programming voltage from the USB programmer when doing ICSP? I don't want the output of the device going to this inout getting a higher than rated voltage.-Keith

  • #2
    I would suggest an diode OR arrangement with both diode cathodes going ro the reset line on the PIC and a pull down resistor. Then 1 of the diodes anodes going to the ICSP programming line. The other anode going to your input signal. The input signal would have to source the current from the 5 volt supply. The pull down resistor can be somewhere around 7.5k to 10 k ohms.
    Dave Purola,
    N8NTA
    EN82fn

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    • #3
      You could also use a removable jumper. Pull the jumper when you program then plug it back in when finished.
      We can crack this cotton PIC'n thang!

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      • #4
        Yeah, I've done that. It's messy in this case because of height restrictions. I'd have to remove the jumper once satisfied.

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