Hi,

In a recent project I had to test for a change of
state on an I/O pin. The code I came up with works
ok, but is a bit clunky. I was wondering if there
is a "standard solution" or a better way.

This is what I did:

tstToggle
  movf  gpio, w         ; get the port data
  andlw b'00000100'     ; isolate the pin (I was interested in bit 2)
  xorwf LPin, w         ; LPin is a register that holds the last pin state

  skpnz                 ; if non-zero, then the pin has toggled
  goto  Next_Bit_of_Code
  comf  LPin, w         ; update the previous value
  andlw b'00000100'
  movwf LPin

  ; Do any other processing here


Next_Bit_of_Code
  ...


I feel that it could be shorter and use only 1 bit to store the
last value.

Any thoughts, anyone?


Regards,


Mike Watson