Interruption

[Bruce]

I'll give it a shot with a simple ON INTERRUPT version.

  x var BYTE
  Switch VAR BIT
  
  TRISA = $FF
  TRISC = 0

  ANSEL = 0            ' A/D disabled (all digital)
  ANSELH = 0
  IOCA.3 = 1           ' int-on-change enabled for RA3
  INTCON = %10001000   ' enable global & int-on-change interrupts

  Switch = 1

  ON INTERRUPT GOTO MyISR
  
mainloop:
  x = 1
  
loops:
  PORTC = x
  pause 500
  if switch = 1 then
     if x == 8 then 
        goto mainloop
     else
        x = x << 1
        goto loops
     endif
  else
    if x == 1 then
       x = 8
       goto loops
    else
       x = x >> 1
      goto loops
    endif
  endif
  GOTO mainloop ' just in case

  DISABLE
MyISR:
  WHILE PORTA.3=0  ' wait for button release (so we can clear the int flag & be
  WEND             ' sure it interrupts on a high-to-low transition)

  Switch = ~Switch ' toggle Switch
  INTCON.0 = 0     ' clear interrupt flag bit
  RESUME
  
  END

There must be ten gozillion ways to do something like this, even without an interrupt, but
it's still handy to at least learn about interrupts.

Note that you could also do something similar by just monitoring the interrupt flag-bit with
global interrupts disabled. You just need to get a tad more creative...;o}

Tap & release the button as fast as you can to see how quickly it reacts.