lab6.asm

时间片系统time slicing system

	#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
__CONFIG   _CP_OFF &  _WDT_OFF &  _XT_OSC & _LVP_OFF & _BODEN_OFF
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						; 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	TRISA						; 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	PORTA						; Return to accessing BANK 0
		BSF	INTCON, GIE
		BSF	INTCON, TMR0IE						; 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'61'						; Preload Timer to 
		MOVWF	TMR0						; count 195 times before roll-over
		RETURN						; return from subroutine
		END