;*************************************************************
;Flashing LEDs 1.
;This program continuously outputs a series of led patterns, 
;using ping-pong hardware. LED patterns are listed within 
;the program.
;TJW 9.11.08  			Tested in simulation 9.11.08
;*************************************************************
;Clock is 800kHz
;Configuration Word: WDT off, power-up timer on, 
;			   code protect off, RC oscillator
;
	list 	p=16F84A
;
;specify SFRs
pcl     equ  02
status  equ  03
trisa   equ  05
portb   equ  06
trisb   equ  06
;
delcntr1	equ 11
delcntr2	equ 12
;
	org 	00
;Initialise
start 	bsf	status,5 	;select memory bank 1
	movlw	B'00011000' ;set port A right for hardware,
	movwf	trisa	;even tho not used in this program. 
	movlw	00
	movwf	trisb	;all port B bits output
	bcf		status,5 	;select bank 0
;
;The “main” program starts here
loop    movlw  B'01010101'
	movwf	portb	;set up new output pattern
	call 	delay
	movlw 	B'10101010'
	movwf	portb	;set up new output pattern
	call 	delay
	goto	loop	;loop again
;
;*************************************************************
;Subroutines
;*************************************************************
;Introduces delay of 500ms approx, for 800kHz clock
delay 	movlw   D'100'
      	movwf   delcntr2
outer	movlw   D'200'	
      	movwf   delcntr1
inner 	nop			
      	nop
      	decfsz  delcntr1,1
      	goto    inner
      	decfsz  delcntr2,1
      	goto    outer
      	return  
;
	end