Файл: Microcontroller Programming. Thi Micro Chip PIC (Julio Sanchez, 2007).pdf

Сделать презентацию

Скачать файл (4,76Мб)

Заказать решение

ВУЗ: Не указан

Категория: Не указан

Дисциплина: Не указана

Добавлен: 14.06.2025

Просмотров: 8607

Скачиваний: 0

ВНИМАНИЕ! Если данный файл нарушает Ваши авторские права, то обязательно сообщите нам.

Interrupts

231

;flash LED ;============================

;Program flashes LED wired to Port-B, line 2 lights:

movlw	b’00000010’	; Mask with bit 1 set
xorwf	PORTB,f	; Complement bit 1
call	long_delay
call	long_delay
call	long_delay
goto	lights

;=======================================================

;Interrupt Service Routine ;=======================================================

;Service routine receives control when there is

;action on pushbutton switch wired to Port-B, line 0 IntServ:

;First test if source is an RB0 interrupt

btfss	INTCON,INTF	; INTF flag is RB0 interrupt
goto	notRB0	; Go if not RB0 origin
; Save context
movwf	old_w	; Save w register
swapf	STATUS,w ; STATUS to w
movwf	old_STATUS	; Save STATUS

;Make sure that interrupt occurred on the falling edge

;of the signal. If not, abort handler

btfsc	PORTB,0	;	Is	bit set?
goto	exitISR	;	Go	if clear

;=========================

;interrupt action ;=========================

;Debounce switch

;Logic:

;Debounce algorithm consists in waiting until the

;same level is repeated on a number of samplings of the

;switch. At this point the RB0 line is clear since the

;interrupt takes place on the falling edge. An initial

;short delay makes sure that spikes are ignored.

movlw	D’10’	;	Number of repetitions
movwf	count2	;	To counter

wait:

;Check to see that port-B bit 0 is still 0

;If not, wait until it changes

btfsc	PORTB,0	; Is bit set?
goto	exitISR	;	Go if bit not 0
; At this point RB0 bit is clear
decfsz	count2,f ; Count this iteration
goto	wait	;	Continue if not zero

; Interrupt action consists of toggling bit 2 of

232

; port-B to turn LED on and off movlw b’00000100’

xorwf PORTB,f ;=========================

;exit ISR ;========================= exitISR:

;Restore context

swapf old_STATUS,w movfw STATUS

swapf old_w,f swapf old_w,w

; Reset,interrupt notRB0:

Chapter 11

;Xoring with a 1-bit produces

;the complement

;Complement bit 2, port-B

;Saved STATUS to w

;To STATUS register

;Swap file register in itself

;re-swap back to w

bcf INTCON,INTF ; Clear INTCON bit 1

retfie ;=======================

;Procedure to delay

;10 machine cycles ;======================= delay:

movlw	D’4’	; Repeat 12 machine cycles
movwf	count1	; Store value in counter
repeat
decfsz	count1,f	; Decrement counter
goto	repeat	; Continue if not 0
return

;=============================

;long delay sub-routine

;(for debugging) ;============================= long_delay

	movlw	D’200’ ; w = 200 decimal
	movwf	J	; J = w
jloop:	movwf	K	; K = w
kloop:	decfsz	K,f	; K = K-1, skip next if zero
	goto	kloop
	decfsz	J,f	; J = J-1, skip next if zero
	goto	jloop
	return
	end

11.4.2 The SleepDemo Program

;File: SleepDemo

;Date: April 25, 2006

Interrupts

233

; Author: Julio Sanchez

;Processor: 16F84A

;Description:

;Program to use the External Interrupt on port RB0

;to terminate the power-down state caused by the

;SLEEP instruction. A pushbutton switch is connected to

;port RB0. The pushbutton generates the interrupt that

;ends the SLEEP conditions.

;Demonstration:

;A LED on port-B, line 1, flashes on and off at 1/2

;second intervals for 20 iterations. At that time the

;program enters the SLEEP condition. Pressing the

;pushbutton switch on line RB0 generates the interrupt

;that ends the SLEEP.

;===========================

;switches ;===========================

;Switches used in __config directive:

;		_CP_ON	Code protection ON/OFF
; *		_CP_OFF
;	*	_PWRTE_ON	Power-up timer ON/OFF

;_PWRTE_OFF

;	_WDT_ON	Watchdog timer ON/OFF
; * _WDT_OFF
;	_LP_OSC	Low power crystal	occilator
; * _XT_OSC		External parallel	resonator/crystal oscillator
;	_HS_OSC	High speed crystal resonator (8 to		10 MHz)
;		Resonator: Murate	Erie CSA8.00MG =	8 MHz
;	_RC_OSC	Resistor/capacitor oscillator (simplest, 20%

error)

;|_____ * indicates setup values

;=========================
; setup and configuration
;=========================
	processor 16f84A
	include	<p16f84A.inc>
	__config	_XT_OSC & _WDT_OFF & _PWRTE_ON & _CP_OFF
;=====================================================
;	variables in PIC RAM
;=====================================================
; Local variables
	cblock	0x0d	; Start of block
	J		; counter J

234		Chapter 11
K		; counter K
count1		; Auxiliary counter
count2		; Second auxiliary counter
old_w		; Context saving
old_STATUS ; Idem
endc
;========================================================
;	m a i n	p r o g r a m
;========================================================
org	0	; start at address 0
goto	main

;

;============================= ; interrupt handler ;=============================

org 0x04 goto IntServ

;=============================

;main program ;============================= main:

;Set up interrupt on falling edge

;by clearing OPTION register bit 6 movlw b’10111111’

option

movlw	b’11111111’	; Set port a			for input
tris	PORTA
movlw	b’00000001’	; Port-B bit			0 is input
tris	PORTB	;	all	others	are output
clrf	PORTB	;	All	port-B	to 0

;============================

;setup interrupts ;============================

;Clear external interrupt flag (INTF = bit 1)

bcf

INTCON,INTF

; Clear flag

;Enable global interrupts (GIE = bit 7)

;Enable RB0 interrupt (INTE = bit 4)

bsf	INTCON,GIE	;	Enable	global int (bit	7)
bsf	INTCON,INTE	;	Enable	RB0 int (bit 4)

;============================

;flash LED 20 times ;============================ wakeUp:

;Program flashes LED wired to port-B, line 2

;20 times before entering the sleep state

movlw	D’20’	;	Number of iterations
movwf	count2	;	To counter

Interrupts		235
lights:
movlw	b’00000010’	; Mask with bit 1 set
xorwf	PORTB,f	; Complement bit 1
call	long_delay
call	long_delay
call	long_delay
decfsz	count2,f ; Decrement counter
goto	lights
; 20 iterations have taken place
sleep
nop		; Recommended!
goto	wakeUp	; Resume execution

;=======================================================

;Interrupt Service Routine ;=======================================================

;The interrupt service routine performs no operation IntServ:

	bcf	INTCON,INTF	; Clear flag
	retfie
;=============================
;	long delay sub-routine
;=============================
long_delay
	movlw	D’200’ ; w = 200 decimal
	movwf	J	; J = w
jloop:
	movwf	K	; K = w
kloop:
	decfsz	K,f	; K = K-1, skip next if zero
	goto	kloop
	decfsz	J,f	; J = J-1, skip next if zero
	goto	jloop
	return