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I/O port irregularity? 68HC11

Discussion in 'Electronic Design' started by bruce varley, Oct 17, 2004.

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  1. bruce varley

    bruce varley Guest

    Hello,

    This is probably becoming a legacy topic. I hope there's someone out there
    who can assist.

    According to the 68HC11 reference manual, Port A PA3-6 can be general
    purpose outputs, or driven by timer output compare functions. If one
    disables the latter then it should simply be a matter of writing to the PA
    register, $1000 to set the pin voltage.

    I find that that works fine for PA4-6, but despite many attempts I can't set
    PA3.

    All the 'obvious' things have been tried. I've reread chapters 7 and 10 in
    the r.m., and AFAICT the registers are set correctly for gen purpose I/O -
    OC1M =TCTL1 = CFORC = 0. The pinout diagrams for E2 and E9 chip variants (I
    use E2) reference an input compare function for the PA3 pin. There's no
    reference to that elsewhere, it could be the problem but I don't know how to
    solve it if it is.

    I need to use this pin as an output. Can anyone assist? TIA
     
  2. timmmmayyy!

    timmmmayyy! Guest

    I`m using the pic877 as an example here but believe you have the same
    problem.
    Pin Ra4 on the pic is a pull down only output. Found this out after making
    24 boards.
    Use a pull up resistor.
    Thanks
    Good luck
     
  3. Rich Grise

    Rich Grise Guest

    RTFM:
    http://www.freescale.com/files/microcontrollers/doc/data_sheet/M68HC11E.pdf
    page 110: DDRA3

    Cheers!
    Rich
     
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