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8051 Reset with membrane keypad

Discussion in 'Electronic Design' started by mpm, Dec 11, 2007.

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  1. mpm

    mpm Guest

    Have not tested it yet, but figured I would ask....

    Can an 8051 be reset directly with a membrane type switch?
    Specifically, the Atmel AT89S52 (but at some point the design /
    availability could mandate some other 8051 derivative part, as yet

    I plan to use a 4.7k / 1uF combination, and simply take Pin-9 high to
    reset it.

    For this particular type of project, I would normally use a uPC that
    either has internal power-up reset on-chip, or maybe even an outboard
    device like a DS1232 or something.

    BUT, if it's acceptable to just use an non-debounced, unconditioned,
    membrane switch to reset the uPC, this particular design could benefit
    from the reduced parts count. Note that I would probably also use a
    software watchdog, and I believe the AT89S52 has a power rail monitor
    for brownout already built-in (which would also have been provided by
    a DS1232 or equiv.)

    What do you think?
  2. Eeyore

    Eeyore Guest

    I think it's fine.

    Include a low value resistor in series with the switch to limit the
    discharge current from the cap.

    1uF sounds a little low btw.

  3. Sounds like it will work, watch out for external noise that could reset it for you.
    You could also use a software reset, jump to 0x0000.

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