> Looking for advice on a way to insure that only one of four push buttons
> is
> active at one time. (IE - prevent multiple button press's) I have 4
> pushbuttons
> on Port A (16F88) and have AND'ed these bits out. The only idea that I've
> tossed
> around so far is to rotate the bits and count them.. If count = 1 then
> only one
> push button is selected. Is there a better way to do this?

Here's a solution to check if one and only one button is pressed. It
doesn't require the buttons to be adjacent.

    MOVF  A,W
    ANDLW BUTTON_MASK
    SKPNZ
     return     ; No buttons are pressed

    MOVWF temp  ; Clear one bit by using x &(x-1)
    ADDLW 0xff  ; W=PORTA-1
    ANDWF temp  ; W=PORTA&(PORTA-1)
    SKPZ
     return     ; More than one button is pressed

    ; temp holds the one and only button press

Scott
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