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can not see input

John Garrelts

Maybe someone can help me out...????

I am having the following problem....
I am using in- and outputs on P1 of a 87C51R+ micro.
As far as I can tell I have correctly set the inputs of the port by sending a "1" to them.
Even though it all seems to function in dscope, it doesn't on the micro board.
example:

sfr trigger = P1^0;
If not mistaken if I have code reading the bit, shouldn't it react in some way..???
eg:
if(trigger == 1){
    ........
}
this problem doesn't allways exist, only on some projects. Just seem to be able to find out what I am doing wrong. Any help appreciated.

Parents
  • 0

    By default, all lines of P1 are set as inputs. The following code:

    if(trigger == 1){
    ........
}

    checks for all bits except bit 0 to be set to 0. If you are really only interested in bit 0, you should probably use the following:

    if(trigger & 0x01){
    ........
}

    Jon

Reply
  • 0

    By default, all lines of P1 are set as inputs. The following code:

    if(trigger == 1){
    ........
}

    checks for all bits except bit 0 to be set to 0. If you are really only interested in bit 0, you should probably use the following:

    if(trigger & 0x01){
    ........
}

    Jon

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