;******************TIMER*****************
; by: Eng'r Roland Michael A. dela Peņa *
;****************************************
        			                     			
	LIST            P=16F84		
	ERRORLEVEL      -302
	#INCLUDE        P16F84.INC    

;****************************************************************************
; REGISTER DEFINITIONS
;****************************************************************************

	CBLOCK	0CH
		TEMPW	  ; TEMP REG BEFORE THE ACCUMULATOR WILL BE USE IN TIMER
		MILLI     ; 100 MILLISECONDS (RTC)
		SEC	  ; ONES FOR SECONDS (RTC)
		SECT	  ; TENS FOR SECONDS (RTC)
		MIN	  ; ONES FOR MINUTES (RTC)
		MINT	  ; TENS FOR MINUTES (RTC)
		HOUR	  ; ONES FOR HOURS (RTC)
		HOURT	  ; TENS FOR HOURS (RTC)
		ENDC
;****************************************************************************
; 		BIT DEFINITIONS
;****************************************************************************
	#DEFINE STRT	PORTA,0		; START BUTTON
	#DEFINE STOP	PORTA,1		; STOP BUTTON
;****************************************************************************
; THIS PART INITIALIZES THE PORTS AND OTHER PHERIPERALS IN MICROCONTROLLER
;****************************************************************************
	ORG 	0000H		; SET POWER ON RESET VECTOR.
	GOTO    INIT
	ORG	0004H		; RESET VECTOR FOR INTERRUPT
	GOTO	ISR

INIT
	BSF 	STATUS,RP0	; SET BANK = 1.
        BCF	OPTION_REG,7	; ENABLE BUILT-IN PULL-UP RESISTORS.
	BCF	OPTION_REG,5	; SET CLOCK SOURCE TO INTERNAL INSTRUCTION CYCLE CLOCK.
	BCF	OPTION_REG,3	; SET PRESCALER TO TMR0.
       	MOVLW 	B'00000000'	; SET ALL PORTB TO OUTPUT
        MOVWF   TRISB           
	MOVLW	B'11111111'	; SET ALL PORTA TO INPUT.
	MOVWF	TRISA		
        BCF 	STATUS,RP0	; SET BANK = 0.
;****************************************************************************
; MAIN ROUTINE (CRYSTAL = 10MHZ)
; 10 HOUR TIMER USING TIMER0 INTERRUPT
;****************************************************************************
START
	; RESERVED FOR PROGRAM LINES
	;
	;
	BTFSC	STRT		; IS START TIMER BUTTON PRESSED?
	GOTO 	STARTIME	; YES.
	GOTO START		; NO.
;**************************************************************
; ENABLING THE INTERRUPT AT TIMER0
;**************************************************************
STARTIME
	BTFSC	STRT
	GOTO 	STARTIME
	MOVLW	d'158'		; LOAD TIMER0 INTERVAL VALUE.
	MOVWF	TMR0		; SET TMR0 = 158 or 98 MORE COUNTS TO OVERFLOW.
	BSF	INTCON,5	; ENABLE TMR0.
        BSF	INTCON,GIE	; TIMER0 IS NOW READY FOR INTERRUPT.
				; TMR0  STARTS TO DECREMENT AFTER GIE = 1.
STARTIME1
	; ADD ANY ROUTINE HERE 
	; LIKE DISPLAY
	;
	BTFSC	STOP		; IS STOP BUTTON PRESSED?
	GOTO 	STOP1		; YES.
	GOTO 	STARTIME1	; NO.
;**************************************************************
; DISABLING THE INTERRUPT AT TIMER0
;**************************************************************	
STOP1
	BTFSC	STOP
	GOTO 	STOP1
	BCF	INTCON,GIE	; DISABLE GIE SO THAT NO INTERRUPT CAN OCCUR
	BCF	INTCON,2	; CLEAR T0IF FLAG
	GOTO 	START
;****************************************************************************
; TIMER SUBROUTINE
;****************************************************************************
ISR
	BCF	INTCON,GIE	; DISABLE GIE SO THAT NO INTERRUPT CAN OCCUR
	BCF	INTCON,2	; CLEAR T0IF FLAG
	MOVWF	TEMPW
	MOVLW	D'158'		; RELOAD TMR0 VALUE
	MOVWF	TMR0
	INCF	MILLI
	MOVLW	d'100'	
	XORWF	MILLI,0
	BTFSS	STATUS,2	; IS 1 SEC OVER?
	GOTO    ISR1		; NO.
	INCF	SEC		; 1 SEC WAS OVER.
	CLRF	MILLI
	MOVLW	d'10'	
	XORWF	SEC,0
	BTFSS	STATUS,2
	GOTO    ISR1
	INCF	SECT
	CLRF	SEC
	MOVLW	d'6'	
	XORWF	SECT,0
	BTFSS	STATUS,2	; IS 1 MIN OVER?
	GOTO    ISR1		; NO.
	INCF	MIN		; YES.

	CLRF	SECT
	MOVLW	d'10'	
	XORWF	MIN,0
	BTFSS	STATUS,2
	GOTO    ISR1	
	INCF	MINT
	CLRF	MIN
	MOVLW	d'6'	
	XORWF	MINT,0
	BTFSS	STATUS,2	; IS 1 HOUR OVER?
	GOTO    ISR1		; NO.
	INCF	HOUR		; YES.
	CLRF	MINT
	MOVLW	d'10'	
	XORWF	HOUR,0
	BTFSS	STATUS,2
	GOTO    ISR1	
	INCF	HOURT
	CLRF	HOUR
	MOVLW	d'10'
	XORWF	HOURT,0
	BTFSS	STATUS,2	; IS 10 HOURS OVER?
	GOTO ISR1
	CLEAR	HOURT
ISR1
	MOVFW	TEMPW
	RETFIE		
	
	END