This code program
W EQU 0
F EQU 1
Z EQU 2
ZERO EQU 2
C EQU 0
CARRY EQU 0
GPWUF EQU 7
;========================
SW0 EQU 0 ;switch names
SW1 EQU 1
SW2 EQU 3
SW3 EQU 4
TFlag EQU 7 ;bit numbers for flags
DBTime EQU 12
;========================
; endef regester
;========================
INDF EQU H'00'
TMR0 EQU H'01'
PCL EQU H'02'
STATUS EQU H'03'
FSR EQU H'04'
OSCCAL EQU H'05'
GPIO EQU H'06'
;=======================
SleepT EQU H'07' ; inactivity counter to allow sleep
Flags EQU H'08' ; storage space for messages
ThisSw EQU H'09' ; current switch status
;=======================
; switch0
LastSw0 EQU H'0A' ; last value - for detecting change
SwState0 EQU H'0B' ; the official (debounced) status
DBTimer0 EQU H'0C' ; counter used during debouncing of the switch
; switch1
LastSw0 EQU H'0D' ; " "
SwState0 EQU H'0E' ; " "
DBTimer0 EQU H'0F' ; " "
; switch2
LastSw0 EQU H'10' ; " "
SwState0 EQU H'11' ; " "
DBTimer0 EQU H'12' ; " "
; switch3
LastSw0 EQU H'13' ; " "
SwState0 EQU H'14' ; " "
DBTimer0 EQU H'15' ; " "
;=====================
ORG H'0200'
ID0 Data H'0000'
ID1 Data H'0000'
ID2 Data H'0000'
ID3 Data H'0003'
;=====================
; MCLRDisabled, NoCodeProtect, NoWatchDog, IntRCOsc
ORG H'0FFF'
CONFIG Data H'000A'
;=====================
ORG H'00'
MOVWF OSCCAL ; store the factory osc. calibration value
Start CLRWDT ; setting up options
MOVLW B'00000010' ; use int clock input, /8 prescaler
OPTION ; pullups on, and wakeup on pin change
BTFSS STATUS,GPWUF ; don't change outputs on a wakeup
CLRF GPIO ; but output 0s on a powerup
MOVLW B'00011011' ; GP0, GP1 , GP3 and GP4 are inputs
TRIS GPIO ; GP2, GP5 are outputs
CLRF SleepT
CLRF Flags
CLRF DBTimer0
CLRF DBTimer1
CLRF DBTimer2
CLRF DBTimer3
BTFSC STATUS,GPWUF ; on wakeup, don't change the switch states
GOTO Main
CLRF LastSw0 ; but if it's a powerup,
CLRF SwState0 ; assume they're all off (open)
CLRF LastSw1
CLRF SwState1
CLRF LastSw2
CLRF SwState2
CLRF LastSw3
CLRF SwState3
;==================
Main CALL DoTime ; need clock 'running'for debounce
CALL Switch0 ; check switch0 position,
CALL Switch1 ; then switch1,
CALL Switch2 ; then switch2,
CALL Switch3 ; and switch2
CLRW ; assume no switch is pressed
MOVF SwState0,F ; check the state of sw0
BTFSS STATUS,Zero ; do nothing if it's not pressed
IORLW B'00000100' ; else set GP2 high
MOVF SwState1,F ; same for sw1
BTFSS STATUS,Zero ; do nothing if it's not pressed
IORLW B'00000100' ; output on GP2
MOVF SwState2,F ; same for sw2
BTFSS STATUS,Zero ; do nothing if it's not pressed
IORLW B'00100000' ; output on GP5
MOVF SwState3,F ; and sw3
BTFSS STATUS,Zero ; do nothing if it's not pressed
IORLW B'00100000' ; with output on GP5
MOVWF GPIO
GOTO Main
;=================
; DoTime
DoTime BTFSS TMR0,7 ; high bit of timer set?
GOTO dt1 ; no - we've overflowed
BSF Flags,TFlag ; yes, set the flag
RETLW 0
dt1 BTFSS Flags,TFlag ; have the timers been serviced?
RETLW 0 ; yes
INCF DBTimer0,F
INCF DBTimer1,F ; no, increment all the timers
INCF DBTimer2,F
INCF SleepT,F
BCF Flags,TFlag ; reset the service flag, and
BTFSS STATUS,Zero ; see if the sleep timer has overflowed
RETLW 1
; There's been no activity for 256*2mS, it's time to sleep
MOVF GPIO,W ; read the current pin status
SLEEP ; and good night
;==================
; Switch0
; GP0
Switch0 CLRF ThisSw ; assume switch is not pressed
BTFSS GPIO,Sw0 ; check sw status
INCF ThisSw,F ; the sw was pressed
; Compare to last state
MOVF LastSw0,W
XORWF ThisSw,W
BTFSS STATUS,Zero ; Zero is set if there's been no change.
; No change since last scan, but are we in a debounce phase?
GOTO sw01
MOVF SwState0,W
XORWF ThisSw,W ; compare present state of sw to the official state
BTFSC STATUS,Zero ; Zero is Clr if they differ (we're in debounce)
GOTO sw02
; Switch is changing, have we gone past the debounce time?
MOVLW DBTime ; get the debounce time
SUBWF DBTimer0,W ; and compare to elapsed
BTFSS STATUS,Carry ; Carry is set if DBTimer >= DBTicks
GOTO sw02
; we've exceeded the debounce time - change the official state of the switch
MOVWF SwState0 ; store current state in SwState
GOTO sw02
; the switch input is changing state - prepare to debounce
sw01 MOVF ThisSw,W
MOVWF LastSw0 ; remember this passes' state
CLRF SleepT ; we've had activity - reset the sleep timer
CLRF DBTimer0 ; and reset the debounce timer
; we're done for this pass...
sw02 BTFSS SwState0,0 ; check the switch state, and
RETLW 0 ; return with 0 if not pressed,
RETLW 1 ; 1 if pressed
; *********************************************
; Switch1
; GP1
Switch1 CLRF ThisSw ; assume switch is not pressed
BTFSS GPIO,Sw1 ; check sw status
INCF ThisSw,F ; the sw was pressed
; Compare to last state
MOVF LastSw1,W
XORWF ThisSw,W
BTFSS STATUS,Zero ; Zero is set if there's been no change
GOTO sw11
; No change since last scan, but are we in a debounce phase?
MOVF SwState1,W
XORWF ThisSw,W ; compare present state of sw to the official state
BTFSC STATUS,Zero ; Zero is Clr if they differ (we're in debounce)
GOTO sw12
; Switch is changing, have we gone past the debounce time?
MOVLW DBTime ; get the debounce time
SUBWF DBTimer1,W ; and compare to elapsed
BTFSS STATUS,Carry ; Carry is set if DBTimer >= DBTicks
GOTO sw12
; we've exceeded the debounce time - change the official state of the switch
MOVF ThisSw,W
MOVWF SwState1 ; store current state in SwState
GOTO sw12
; the switch input is changing state - prepare to debounce
sw11 MOVF ThisSw,W
MOVWF LastSw1 ; remember this passes' state.
CLRF SleepT ; we've had activity - reset the sleep timer
CLRF DBTimer1 ; and reset the debounce timer
; we're done for this pass...
sw12 BTFSS SwState1,0 ; check the switch state, and
RETLW 0 ; return with 0 if not pressed,
RETLW 1 ; 1 if pressed
; *********************************************
; Switch2
; GP3
Switch2 CLRF ThisSw ; assume switch is not pressed
BTFSS GPIO,Sw2 ; check sw status
INCF ThisSw,F ; the sw was pressed
; Compare to last state
MOVF LastSw2,W
XORWF ThisSw,W
BTFSS STATUS,Zero ; Zero is set if there's been no change
GOTO sw21
; No change since last scan, but are we in a debounce phase?
MOVF SwState2,W
XORWF ThisSw,W ; compare present state of sw to the official state
BTFSC STATUS,Zero ; Zero is Clr if they differ (we're in debounce)
GOTO sw22
; Switch is changing, have we gone past the debounce time?
MOVLW DBTime ; get the debounce time
SUBWF DBTimer2,W ; and compare to elapsed
BTFSS STATUS,Carry ; Carry is set if DBTimer >= DBTicks
GOTO sw22
; we've exceeded the debounce time - change the official state of the switch
MOVF ThisSw,W
MOVWF SwState2 ; store current state in SwState
GOTO sw22
; the switch input is changing state - prepare to debounce
sw21 MOVF ThisSw,W
MOVWF LastSw2 ; remember this passes' state
CLRF SleepT ; we've had activity - reset the sleep timer
CLRF DBTimer2 ; and reset the debounce timer
; we're done for this pass...
sw22 BTFSS SwState2,0 ; check the switch state, and
RETLW 0 ; return with 0 if not pressed,
RETLW 1 ; 1 if pressed
; *********************************************
; Switch3
; GP4
Switch3 CLRF ThisSw ; assume switch is not pressed
BTFSS GPIO,Sw3 ; check sw status
INCF ThisSw,F ; the sw was pressed
; Compare to last state
MOVF LastSw3,W
XORWF ThisSw,W
BTFSS STATUS,Zero ; Zero is set if there's been no change
GOTO sw31
; No change since last scan, but are we in a debounce phase?
MOVF SwState3,W
XORWF ThisSw,W ; compare present state of sw to the official state
BTFSC STATUS,Zero ; Zero is Clr if they differ (we're in debounce)
GOTO sw32
; Switch is changing, have we gone past the debounce time?
MOVLW DBTime ; get the debounce time
SUBWF DBTimer3,W ; and compare to elapsed
BTFSS STATUS,Carry ; Carry is set if DBTimer >= DBTicks
GOTO sw32
; we've exceeded the debounce time - change the official state of the switch
MOVF ThisSw,W
MOVWF SwState3 ; store current state in SwState
GOTO sw32
; the switch input is changing state - prepare to debounce
sw31 MOVF ThisSw,W
MOVWF LastSw3 ; remember this passes' state
CLRF SleepT ; we've had activity - reset the sleep timer
CLRF DBTimer3 ; and reset the debounce timer
; we're done for this pass...
sw33 BTFSS SwState3,0 ; check the switch state, and
RETLW 0 ; return with 0 if not pressed,
RETLW 1 ; 1 if pressed
END