; TUTA4.ASM ; using	aliases, bit names and conditional loops
        list	p=p16f877
        radix	hex
	include "p16f877.inc"
	__CONFIG _HS_OSC & _WDT_OFF & _LVP_OFF	; high speed >4MHz OSC 
						; disable watchdog timer

#DEFINE	PAGE0 BCF STATUS,5
#DEFINE	PAGE1 BSF STATUS,5

COUNT	EQU 	0x20	; Counter storage
NCOUNT	EQU 	0x21	; Count Down storage register
MCOUNT	EQU 	0x22	; Count Down storage register
OCOUNT	EQU 	0x23	; Count Down storage register
SHIFT	EQU 	0x24	; Temporary pattern register
W	EQU 	0	; Working register flag
F	EQU 	1	; File register flag
C	EQU 	0	; Carry flag

	ORG 	0	; Reset vector
	CALL 	5	; CALL start of program
       	ORG 	4	; Interrupt vector
	CALL 	5	; CALL start of program
       	ORG 	5	; Start of program memory

       	CLRF	PORTA	 ; clear Port A data register
       	CLRF	PORTB	 ; clear Port B data register
       	CLRF	PORTC	 ; clear Port C data register
       	CLRF 	PORTD	 ; clear Port D data register
       	CLRF 	PORTE	 ; clear Port E data register

       	PAGE1		 ; PAGE1

       	CLRF	TRISA	 ; set all Port A as output (clear direction reg)
       	CLRF 	TRISB	 ; set all Port B as output (clear direction reg)
       	CLRF 	TRISC	 ; set all Port C as output (clear direction reg)
       	CLRF 	TRISD	 ; set all Port D as output (clear direction reg)
       	CLRF 	TRISE	 ; set all Port E as output (clear direction reg)

       	PAGE0		 ; PAGE0

	
	BCF 	STATUS,C	; disable carry flag
	MOVLW 	B'00000001'	; initial bit pattern
	MOVWF 	SHIFT		; store pattern
	

;
; This will cause my pants to sequence through the active
; ports B,C,D. These ports were specifically choosen, and 
; the wires run in such a way to make the programming 
; ridiculously easy. Simply rotating a bit.
;

SEQALL	MOVF	SHIFT,W		; retreive latest bit pattern
	MOVWF	PORTB		; turn on a yellow wire
	CALL	PAUSE 		; approx. 1 second delay
        CLRF	PORTB		; clean up glowing wire
	MOVF	SHIFT,W		; retreive latest bit pattern
	MOVWF	PORTC		; turn on a red wire
	CALL	PAUSE 		; approx. 2 second delay
        CLRF 	PORTC		; clean up glowing wire
	MOVF	SHIFT,W		; retreive latest bit pattern
	MOVWF 	PORTD		; turn on a blue wire
	CALL 	PAUSE 		; approx. 1 second delay
        CLRF 	PORTD		; clean up glowing wire
	RLF	SHIFT,F		; move onto next wire all colors
	GOTO 	SEQALL		; again, next bit

;
; Delay
;
PAUSE	MOVLW	0xFF
	MOVWF	MCOUNT
LOADN	MOVLW	0xFF
	MOVWF	NCOUNT
DECO	NOP
	NOP
	DECFSZ	OCOUNT,F
	GOTO	DECO
	DECFSZ	MCOUNT,F
	GOTO	LOADN
	RETURN
END