; Sigarch.asm
; Simple PIC16F84 Program to flash LEDs

; Include the header file for our target chip
	#include "p16f84.inc"

; First line, declare that we want a 16F84 PIC
; and that our numbers will be in Hexadecimal
; unless otherwise noted
	LIST P=16f84, R=HEX

; Tell the programmer what options we want to use
; In this case:
; _WDT_OFF -- Watchdog Timer Off
; _XT_OSC -- Crystal Oscillator
; _CP_OFF -- Code Protect Off

	__CONFIG _WDT_OFF & _XT_OSC & _CP_OFF

; Variable Declarations
; Here we assign memory locations for our variables

; assign counter1 to register 0x20
counter1	EQU	0x20
; assign counter2 to register 0x21
counter2	EQU	0x21

; First column is always for labels.  Anything in the first
; column will be interpreted by the assembler as a label

Start
	CLRF	PORTB			; Initialize Port B
	CLRW				; Clear W register
	BSF	STATUS,RP0		; Select Register Bank 1
	MOVWF	TRISB			; Set B to all outputs
	BCF	STATUS,RP0		; select Register Bank 0

	CLRF	counter1		; clear counter1 -> register 0x20
	CLRF	counter2		; clear counter2 -> register 0x21

Outer_Loop
	INCF	PORTB,F			; increment port B
Delay_Loop
	DECFSZ	counter1,f		; DECrement File register and Skip if Zero
					; skips next instruction if counter1 is 0
					; after it decrements counter1
	GOTO	Delay_Loop		; goes back to Delay_Loop
	DECFSZ	counter2,f		; skips next instruction if counter2 is 0
	GOTO	Delay_Loop		; goes back to Delay Loop
					; Net effect of last 4 instructions is to delay
					; by about 100ms 
	GOTO	Outer_Loop		; Go back to Outer_Loop and repeat indefinitely

	END				; End of program