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
								; Clear the TMR0 中断 condition
								; Add 1 to LEDCtr
								; Add 1 to PiezoCtr
								; Reload the Timer for accurate timing
								; Macro to context restore when leaving ISR
								; Return from 中断

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

								; Turn on GIE and TMR0 中断
		movwf	INTCON			;  "

LEDTest
		movlw	D'8'			; Test LED1 Counter Value for overflow
								;  by subtracting 8 from it.  Leave result in W
								; Test for 0 to determine if equal
		goto	NotEqual1		; If counter is not 8, test if LED should be on or off
								; If counter is 8, it is reset to 0
NotEqual1
								; Test LED counter against "On" time
								;  by subtracting 3 from it.  Leave result in W
								; Test for negative value to determine if less than 3
		goto	TurnOffLED		; if 3 or more, goto LEDOff Code
TurnOnLED
								; 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
								; Test Piezo Counter Value
								;  by subtracting 30 from it.  Leave result in W
								; Test for 0 to determine if equal
		goto	NotEqual2		; If counter is not 30, test if LED should be on or off
								; If counter is 30, it is reset to 0
NotEqual2
								; Test Piezo Counter against "On" time
								;  by subtracting 10 from it.  Leave result in W
								; Test for negative value to determine if less than 3
		goto	TurnOffPiezo 	; if 10 or more, goto LEDOff Code
TurnOnPiezo
								; Turn on LED1
								; Turn on Piezo (by turning on CCP1)
		goto	LEDTest			; manage tasks by returning to top of list
TurnOffPiezo
								; 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
								; Preload Timer to 
								; count 195 times before roll-over
								; return from subroutine
		END