title  "First Application - Light an LED and Poll a Button."
;
;  This Code Simply Lights an LED and polls a button and turns
;   on another LED when it is pressed.
;
;
;  Hardware Notes:
;   Reset is tied directly to Vcc and PWRT is Enabled.
;   The PIC is a 16F84 Running at any speed.
;   PortB.0 is Connected to a Button that pulls down to Ground when Pressed
;   PortB.1 is Connected to an LED which is Pulled to Ground ("On" LED)
;   PortB.2 is Connected to an LED which is Pulled to Ground ("Button" LED)
;
;  Myke Predko
;  99.05.18
;
  LIST P=16F84, R=DEC
  errorlevel 0,-305
  INCLUDE "p16f84.inc"

;  Register Usage
 CBLOCK 0x00C                   ;  Start Registers at End of the Values
 ENDC


 PAGE
 __CONFIG _CP_OFF & _XT_OSC & _PWRTE_ON  & _WDT_OFF
                                ;  Note that the WatchDog Timer is OFF
;  First Application - Turn on LED and poll the Button.

  org    0

  movlw  0x0FD                  ;  Turn on LED on RB1 When Output Enabled
  movwf  PORTB

  bsf    STATUS, RP0
  bcf    TRISB ^ 0x080, 1       ;  Enable RB1 for Output
  bcf    TRISB ^ 0x080, 2       ;  Enable RB2 for Output
  movlw  0x07F                  ;  Enable Internal Pull-Ups
  movwf	 OPTION_REG ^ 0x080
  bcf    STATUS, RP0

Loop

  btfsc  PORTB, 0               ;  Is the Button Pressed?
   goto  ButtonUp               ;   No, Light Off

  bcf    PORTB, 2               ;  Turn Light On

  goto   Loop

ButtonUp                        ;  Button Up, Turn Light Off

  bsf    PORTB, 2

  goto   Loop


  end