lab6.asm

pic单片机资料

	#INCLUDE p16F877A.inc		; Include the standard definitions
	#INCLUDE 701PIC.inc		; Include MACROs from MASTER’s 03, PIC 102 class
	#DEFINE DEVICE_FREQ_HZ D'4000000'  ; Needed by Piezo series macros

LEDCtr	EQU	0x30		; Counter for LED timing
PiezoCtr	EQU	0x31		; Counter for Piezo timing

		ORG	H'00'		; Reset Vector
Start
		goto	Initialize		; Jump to Initialization code

		ORG	H'04'		; 中断 Vector
ISR
		ISRSave			; Macro to context save in ISR
		bcf	INTCON,TMR0IF	; Clear the TMR0 中断 condition
		incf	LEDCtr,F		; Add 1 to LEDCtr
		incf	PiezoCtr,F		; Add 1 to PiezoCtr
		call	DoReloadTimer	; Reload the Timer for accurate timing
		ISRRestore		; Macro to context restore when leaving ISR
		retfie			; Return from 中断

Initialize
		LEDOff	0		; Turn off both LEDs
		LEDOff	1		;  "
		clrf	LEDCtr		; Initialze Task Couters to 0
		clrf	PiezoCtr		;  " (both LED and Piezo)
		LEDEnable   H'FC'		; MACRO to setup I/O port to drive LEDs RB1 and RB0
		PiezoEnable D'500'		; 500 Hz Beep when PiezoOn is used
		call	DoReloadTimer 	; Preload the timer for appropriate time delay
		BANKSEL	OPTION_REG	; set banking to access OPTION_REG in bank 1
		movlw	B'11000111'	; Set up TMR0 for 256 prescale and 
		movwf	OPTION_REG	;  internal clock mode
		BANKSEL	PORTB		; Return to accessing BANK 0

		movlw	B'10100000'	; Turn on GIE and TMR0 中断
		movwf	INTCON		;  "

LEDTest
		movlw	D'8'		; Test LED1 Counter Value for overflow
		subwf	LEDCtr,W		;  by subtracting 8 from it.  Leave result in W
		btfss	STATUS,Z		; Test for 0 to determine if equal
		goto	NotEqual1		; If counter is not 8, test if LED should be on or off
		clrf	LEDCtr		; If counter is 8, it is reset to 0
NotEqual1
		movlw	D'3'		; Test LED counter against "On" time
		subwf	LEDCtr,W		;  by subtracting 3 from it.  Leave result in W
		btfsc	STATUS,C		; Test for negative value to determine if less than 3
		goto	TurnOffLED	; if 3 or more, goto LEDOff Code
TurnOnLED
		LEDOn	0		; else, Turn on LED 0 since counter is less than 3 
		goto	PiezoTest		; LED Testing done, goto PiezoTest
TurnOffLED
		LEDOff	0		; Turn off LED since counter is 3 or more (up to 7)
					; LED Testing now done, so fall into PiezoTest

PiezoTest
		movlw	D'30'		; Test Piezo Counter Value
		subwf	PiezoCtr,W		;  by subtracting 30 from it.  Leave result in W
		btfss	STATUS,Z		; Test for 0 to determine if equal
		goto	NotEqual2		; If counter is not 30, test if LED should be on or off
		clrf	PiezoCtr		; If counter is 30, it is reset to 0
NotEqual2
		movlw	D'10'		; Test Piezo Counter against "On" time
		subwf	PiezoCtr,W		;  by subtracting 10 from it.  Leave result in W
		btfsc	STATUS,C		; Test for negative value to determine if less than 3
		goto	TurnOffPiezo 	; if 10 or more, goto LEDOff Code
TurnOnPiezo
		LEDOn	1		; Turn on LED1
		PiezoOn			; Turn on Piezo (by turning on CCP1)
		goto	LEDTest		; manage tasks by returning to top of list
TurnOffPiezo
		LEDOff	1		; Turn off LED1
		PiezoOff			; Turn off Piezo (by turning off CCP1)
		goto	LEDTest		; manage tasks by returning to top of list

; Subroutine to reload TMR0
DoReloadTimer
		movlw	D'256' - D'195'	; Preload Timer to 
		movwf	TMR0		; count 195 times before roll-over
		return			; return from subroutine
		END