;******************************************************
;*               TM0_INT.ASM
;* 1秒鐘計時中斷，PORTC外接LED全亮後從0遞增
;******************************************************
			list p=16F877		
#include 		<p16f877.inc>
;
VAL_US		equ	.249			; 1ms delay 給定初值
VAL_MS		equ	.250			; 呼叫1ms Delay之次數
count			equ	0x20			; 1ms delay 變數位址
count_ms		equ	0x21   		 ; 呼叫1ms Delay之變數位址.
number		equ	0x22
;
;******  程式開始 *********************
			org 	0x00			; reset vector
			nop				; Reserve for MPLAB-ICD
			goto	start
			org	0x04
			goto	isr
start:	
			clrw
			clrf		PCLATH
			banksel	TRISC	; Select to bank1
			clrf		TRISC	; PORTC = Output
			banksel 	PORTC 	; Select to bank0
			clrf		PORTC		; Clear PORTC
			banksel	OPTION_REG
			movlw	b'00000011'
			movwf	OPTION_REG
			bsf		INTCON,GIE
			bsf		INTCON,T0IE
			banksel	TMR0
			movlw	.6
			movwf	TMR0
			movwf	number

inc:			
			incf		PORTC,f
			call		delay_250ms
			goto		inc
isr:			
			incfsz		number
			goto		isr_end
			movlw	.6
			movwf	number
			movlw 	B'11111111'
			movwf	PORTC
			call		delay_250ms
isr_end:
			movlw	.6
			movwf	TMR0
			bcf	INTCON,T0IF
			retfie

;-------- 250 ms delay routine ----------
delay_250ms:	
			movlw	VAL_MS		 
		movwf	count_ms
loop_ms		call 	delay_1ms
			decfsz	count_ms,f
			goto	loop_ms
		return
;
;-------- 1 ms delay routine -----------
delay_1ms:
			nop			 
		movlw	VAL_US		 		
			movwf	count
dec_loop	nop
			decfsz	count,f
		goto 	dec_loop
			return
;	
			end