;*************************************************************
;FLASHING LEDs!
;This program continuously outputs a series of led patterns, 
;using pingpong hardware.
;TJW 5.3.05  				Tested in simulation 11.3.05
;*************************************************************
;Clock is 1MHz
;Configuration Word: WDT off, power-up timer on, 
;			   code protect off, RC oscillator
;
	list 	p=16F84A
;
;specify SFRs
pcl     equ  02
status  equ  03
porta   equ  05
trisa   equ  05
portb   equ  06
trisb   equ  06
;
pointer equ 10	
delcntr1	equ 11
delcntr2	equ 12
;
	org 	00
;Initialise
start	bsf	status,5 	;select memory bank 1
	movlw	B'00011000'
	movwf	trisa		;port A according to above pattern 
	movlw	00
	movwf	trisb		;all port B bits output
	bcf	status,5 	;select bank 0
;
;The “main” program starts here
	movlw 00		;clear all bits in port A
	movwf porta
	movwf	pointer	;also clear pointer
loop	movf	pointer,0	;move pointer to W register
	call table
	movwf	portb		;move W register, updated from table SR, to port B
	call delay
	incf pointer,1
	btfss pointer,3	;test if pointer has incremented to 8
	goto	loop	      ;if not, just loop again
;here if pointer needs to be cleared 
	movlw 00		
	movwf	pointer	;clear pointer to start over
	goto loop
;
;*************************************************************
;Subroutines
;*************************************************************
;Introduces delay of 500ms approx, for 1 MHz clock
delay movlw D'100'
      movwf delcntr2
outer	movlw D'250'	;
      movwf delcntr1
inner nop			
      nop
      decfsz delcntr1,1
      goto 	inner
      decfsz delcntr2,1
      goto 	outer
      return  

;Holds Lookup Table
table	addwf pcl,1
	retlw 23
	retlw 3f
	retlw 47
	retlw 7f
	retlw 0a2
	retlw 1f
	retlw 03
	retlw 67
;
	end