;
;**********************************************************************************************************************
;task3.asm by James Walmsley (C)2006 [worm.me.uk]
;**********************************************************************************************************************
;

;
;**********************************************************************************************************************
;SET-UP Assembler for PIC, and CHANGE PIC SETTINGS
;**********************************************************************************************************************
;

	include”P16F877.INC”		;include the pic 16f877 assembly definitions

TIMREG	EQU	H’0020'			;Create a register called TIMREG at register address Hex 0020
TIMREG1	EQU	H’0021'			;Create a register called TIMREG1 @ register address Hex 0021

delval	EQU	H’00FF’ 		;Create a variable called delval with the Hex value of 00FF (255)
delval1	EQU	H’00FF’ 		;Create a variable called delval with the Hex value of 00FF (255)


banksel	TRISD 				;Change selected bank to TRISD
clrf 	PORTD 				;Set PORTD to be an output
banksel	PORTD 				;Change selected bank to PORTD

;
;**********************************************************************************************************************
;START OF MAIN PROGRAM
;**********************************************************************************************************************
;

start	movlw	0			;Move literal value of 0 into the working register (W-Register)
movwf	PORTD 				;Move Value of W-Register to PORTD (in this case turning all LEDs off)

loop	incf	PORTD,f			;Define a loop, update the LEDs by incrementing PORTD
call	delay 				;Call up a sub-routine called delay (Found below)
	nop 				;Use the no-operation instruction to waste 1 clock cycle
					;The program counter is therefore increased by 1 instruction count
goto	loop 				;Return to the start of loop (as labelled)

;
;**********************************************************************************************************************
;END OF MAIN PROGRAM & Start of Sub-routines, and Break-points
;**********************************************************************************************************************
;

delay	movlw 	delval			;Start of delay sub-routine, load w-register with value in delval variable
movwf	TIMREG				;Move the delval (from the w-register) value into TIMREG

time	call	delay1 			;Create breakpoint called time & call next delay(1) routine
	decfsz	TIMREG,f 		;Subtract 1 from TIMREG or skip over next instruction if 0
goto 	time				;Return to the time label
	return				;Finish the delay sub-routine and return to main code

delay1	movlw	delval1			;Start of delay1 sub-routine, load w-register with value in delval1 variable
movwf	TIMREG1				;Move the delval1 (from the w-register) value into TIMREG1

time1	decfsz	TIMREG1,f		;Subtract 1 from TIMREG or skip over next instruction if 0
goto	time1 				;Return to the time1 label
	return
	
	end 				;End of Program (leaving 1 more line after this)