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18F67K40 wont reset

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  • 18F67K40 wont reset

    Having trouble trying to reset an 18F67K40 using software (@ RESET command) or hardware via MCLR pin. If power is removed and reconnected, device functions as it should. If I try any other method of reset the device behaves differently and code doesn't run.

    Any ideas?

    Andy

  • #2
    Andy, I use the "RESET" directive all the time for a software reset function. The MCLR pin should also work as expected if the MCLRE is enabled thru the configuration statement of .CONFIG2. Also, what resistance value do you have from MCLR and VDD?
    Dave Purola,
    N8NTA
    EN82fn

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    • #3
      To add to David's comments, there's usually very little difference in the different forms of reset... almost all the registers are set the same.

      Hardware-wise, PON will generate a Powerup timer delay (if enabled by config PWRT) and an Oscillator startup delay (depending on the osc config mode setting). You could try adding a 100msec delay at startup and see if that changes anything.

      @RESET or MCLR won't re-initialize any external hardware (lcd's, i2c, etc), so that's something to consider also.

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      • #4
        Thanks for the replies so far.

        I have used @RESET on multiple occasions and the results were as expected. In this case something is different. The program response is not the same as when on power up.

        Tumbleweed has given me some ideas on where to look. I will keep investigating......

        Andy

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        • #5
          Problem Resolved!

          It was a coding error which fooled me into believing the soft reset wasn't functioning properly. As tumbleweed suggested, the fault was caused by a failure to re-initialize some external hardware.

          Again, thanks for all of the input.

          Andy

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