PIC ile darkroom timer

ilker_32 · 23 Temmuz 2009, 12:26:55


;-------------------------------------------------------------------------;
;                             Darkroom Timer                              ;
;               April '99  Stan Ockers (ockers@anl.gov)                   ;
;                  circuit diagram in CNTDN.PCX                           ;
;                further description in CNTDN.TXT                         ;
;                                                                         ;
;       Counts down from 0-99 min and 0-59 sec giving an alarm at 0       ;
;     initial counts are held in data EEPROM setable with one button      ;
;                                                                         ;
;  RBO-RB3 to bases of transistors connect to common cathode of displays. ;
;  RA0-RA3 to 1,2,4,8 BCD inputs of CD4511 7 segment latch and driver.    ;
;  RB7 to start pushbutton used to start countdown and silence alarm.     ;
;  RB6 goes to time set pushbutton use to sucessively set the digits.     ;
;  RA4 with pull-up resistor goes to PB to select from 15 starting counts ;
;  RB4 and RB5 go to speaker which gives an alarm.                        ;
;-------------------------------------------------------------------------;
 
 
  LIST  P=16F84
  #INCLUDE "p16f84.inc"
 
;-------------------------------------------------------------------------;
;    Here we define our own personal registers and give them names        ;
;-------------------------------------------------------------------------;
 
SEC       EQU H'0C'          ; this register holds the value of seconds
SEC10     EQU H'0D'          ; holds value of 10's of seconds
MIN       EQU H'0E'          ; holds value of minutes
MIN10     EQU H'0F'          ; holds value of 10's of minutes
DIGCTR    EQU H'10'          ; 8 bit counter, only 2 lowest bits actually used
DIGIT     EQU H'11'          ; hold digit number to access table
INTCNT    EQU H'12'          ; counts # interrupts to determine when 1 sec up
FUDGE     EQU H'13'          ; allows slight adjustment every 7 interrupts
RUNFLG    EQU H'14'          ; bit 0 only, tells if countdown in progress 
W_TEMP    EQU H'15'          ; temporarily holds value of W
STATUS_TEMP EQU H'16'        ; temporarily holds value of STATUS
SECNT     EQU H'17'          ; used in counting 50, 20 msec delays for 1 sec
CNTMSEC   EQU H'18'          ; used in timing of milliseconds
ALARM     EQU H'19'          ; bit 0 only, used as flag for when to alarm
OFFSET    EQU H'1A'          ; hold offset of address in EEPROM
 
;-------------------------------------------------------------------------;
;    Here we give names to some numbers to make their use more clear      ;
;-------------------------------------------------------------------------;
 
   #DEFINE   START_PB  D'7'
   #DEFINE   SET_PB    D'6'
   #DEFINE   SELECT_PB D'4'
   #DEFINE   RB4       D'4'
   #DEFINE   RB5       D'5'
 
 
;-------------------------------------------------------------------------;
;         We set the start of code to orginate a location zero            ;
;-------------------------------------------------------------------------;
 
      ORG 0
 
            GOTO MAIN                  ; jump to the main routine
            NOP                        
            NOP                        
            NOP                        
            GOTO INTERRUPT             ; interrupt routine
 
;-------------------------------------------------------------------------;
;    This table is used to get a bit pattern that will turn on a digit    ;
;-------------------------------------------------------------------------;
 
BITPAT      ADDWF PCL,f                ; get bit pattern for transistors
            RETLW H'0E'                ; a low, (0), turns the transistor on  
            RETLW H'0D'                  
            RETLW H'0B'                  
            RETLW H'07'                  
 
;-------------------------------------------------------------------------;
;          Initialization routine sets up ports and timer                 ;
;-------------------------------------------------------------------------;
 
INIT        MOVLW H'C0'                ; PB6 & PB7 inputs all others outputs
            TRIS PORTB                 
            MOVLW H'10'                ; Port RA4 input, others outputs
            TRIS PORTA                 
            MOVLW H'03'                ; prescaler on TMR0 and 1:16
            OPTION                     
            MOVLW H'A0'                ; GIE & T0IE set T0IF cleared
            MOVWF INTCON               
            MOVLW H'F4'                ; initialize INTCNT
            MOVWF INTCNT               
            MOVLW H'06'                ; initialize FUDGE
            MOVWF FUDGE                
            CLRF OFFSET                ; initialize OFFSET
            RETURN                     
 
;-------------------------------------------------------------------------;
;   This is the interrupt routine that is jumped to when TMR0 overflows   ;
;-------------------------------------------------------------------------;
 
INTERRUPT   MOVWF W_TEMP               ; save W
            SWAPF STATUS,W             ; save status
            MOVWF STATUS_TEMP          ; without changing flags
            INCF DIGCTR,f              ; next digit #
            MOVF DIGCTR,W              ; get it into W
            ANDLW H'03'                ; mask off 2 lowest bits
            MOVWF DIGIT                ; save it for later
            ADDLW H'0C'                ; point at register to display
            MOVWF FSR                  ; use as pointer
            MOVF INDF,W                ; get value of reg pointed to into W
            MOVWF PORTA                ; output to CD4511
            MOVF DIGIT,W               ; recall digit #
            CALL BITPAT                ; get bit pattern
            MOVWF PORTB                ; select transistor
            DECFSZ INTCNT,f            ; finished 1 sec ?
            GOTO RESTORE               ; not yet, return and enable inter.
            CALL EVERYSEC              ; go to every second routine
            MOVLW H'F4'                ; reset INTCNT to normal value
            MOVWF INTCNT               
            DECFSZ FUDGE,f             ; time for fudge?
            GOTO RESTORE               ; not yet, continue on
            MOVLW H'06'                ; reset FUDGE to 6
            MOVWF FUDGE                
            INCF INTCNT,f              ; INTCNT to 245
RESTORE     SWAPF STATUS_TEMP,W        ; get original status back
            MOVWF STATUS               ; into status register
            SWAPF STATUS_TEMP,f        ; old no flags trick again
            SWAPF STATUS_TEMP,W        ; to restore W
            BCF INTCON,T0IF            ; clear the TMR0 interrupt flag
            RETFIE                     ; finished
 
;-------------------------------------------------------------------------;
;       This routine is called by the interrupt routine every second      ;
;-------------------------------------------------------------------------;
 
EVERYSEC    BTFSS RUNFLG,0             ; return if runflg not set
            RETURN                     
            DECF SEC,f                 ; decrement seconds digit
            INCFSZ SEC,W               ; test for underflow
            GOTO CKZERO                
            MOVLW H'09'                ; reset sec to 9
            MOVWF SEC                  
            DECF SEC10,f               ; decrement SEC10
            INCFSZ SEC10,W             ; check underflow
            GOTO CKZERO                
            MOVLW H'05'                  
            MOVWF SEC10                
            DECF MIN,f                 
            INCFSZ MIN,W               
            GOTO CKZERO                
            MOVLW H'09'              
            MOVWF MIN                  
            DECF MIN10,f               
CKZERO      MOVF SEC,f                 ; test SEC for zero
            BTFSS STATUS,Z             
            RETURN                     
            MOVF SEC10,f               ; check SEC10 for zero
            BTFSS STATUS,Z             
            RETURN                     
            MOVF MIN,f                 ; check MIN for zero
            BTFSS STATUS,Z             
            RETURN                     
            MOVF MIN10,f               ; check MIN10 for zero
            BTFSS STATUS,Z             
            RETURN                     
            CLRF RUNFLG                ; stop the countdown
            BSF ALARM, 0               ; set the alarm flag
            RETURN                     
 
;-------------------------------------------------------------------------;
;          This is a routine to read a byte from the data EEPROM          ;
;-------------------------------------------------------------------------;
 
READEE      MOVWF EEADR                ; set up eeprom address from W
            BSF STATUS,RP0             ; change to page 1
            BSF EECON1,RD              ; set the read bit
            BCF STATUS,RP0             ; back to page 0
            MOVF EEDATA,W              ; return value in W
            RETURN                     
 
;-------------------------------------------------------------------------;
;         This routine fills the display registers from data EEPROM       ;
;-------------------------------------------------------------------------;
 
GETEE       MOVLW H'01'                ; EEprom location 1 +
            ADDWF OFFSET,W             ; offset from start 
            CALL READEE                ; into W
            MOVWF SEC                  ; into SEC register
            MOVLW H'02'                ; location 2 +
            ADDWF OFFSET,W             ; offset from start 
            CALL READEE                ; into W
            MOVWF SEC10                ; into SEC10 register
            MOVLW H'03'                ; location 3 +
            ADDWF OFFSET,W             ; offset from start 
            CALL READEE                ; into W
            MOVWF MIN                  ; into MIN register
            MOVLW H'04'                ; location 4 +
            ADDWF OFFSET,W             ; offset from start 
            CALL READEE                ; into W
            MOVWF MIN10                ; into MIN10 register
            RETURN                     
 
;-------------------------------------------------------------------------;
;              This routine writes a byte to data EEPROM                  ;
;-------------------------------------------------------------------------;
 
WRITEEE     BSF STATUS,RP0             ; set up EEADR and EEDATA first
            CLRF EECON1                
            BSF EECON1,WREN            ; enable write
            MOVLW H'55'                ; magic sequence
            MOVWF EECON2               
            MOVLW H'AA'                  
            MOVWF EECON2               
            BSF EECON1,WR              
EELOOP      BTFSC EECON1,WR            ; wait for WR to go low
            GOTO EELOOP                ; not yet
            BSF EECON1,WREN            
            BCF EECON1,EEIF            ; clear the interrupt flag
            BCF STATUS,RP0             ; return to page 0
            RETURN                     
 
;-------------------------------------------------------------------------;
;         This routine puts display registers into data EEPROM            ;
;-------------------------------------------------------------------------;
 
PUTEE       MOVF SEC,W                 ; put digit registers into EEprom
            MOVWF EEDATA               
            MOVLW H'01'                ; EEPROM location 1 +  
            ADDWF OFFSET,W             ; offset from start 
            MOVWF EEADR                
            CALL WRITEEE               
            MOVF SEC10,W               
            MOVWF EEDATA               
            MOVLW H'02'                ; EEPROM location 2 +  
            ADDWF OFFSET,W             ; offset from start 
            MOVWF EEADR                
            CALL WRITEEE               
            MOVF MIN,W                 
            MOVWF EEDATA               
            MOVLW H'03'                ; EEPROM location 3 +  
            ADDWF OFFSET,W             ; offset from start 
            MOVWF EEADR                
            CALL WRITEEE               
            MOVF MIN10,W               
            MOVWF EEDATA               
            MOVLW H'04'                ; EEPROM location 4 +  
            ADDWF OFFSET,W             ; offset from start 
            MOVWF EEADR                
            CALL WRITEEE               
            RETURN                     
 
;-------------------------------------------------------------------------;
;         This is the main routine, the program starts here               ;
;-------------------------------------------------------------------------;
 
MAIN        CALL INIT                  ; set up ports etc.
 
;-------------------------------------------------------------------------;
;           We will return to this point when alarm is shut off.          ;
;-------------------------------------------------------------------------;
 
EE2D        CALL GETEE                 ; put eeprom in display regs.
            BCF RUNFLG, 0              ; clear run flag so no countdown
            BCF ALARM, 0               ; clear alarm flag
            CALL WAITSTARTUP           ; wait till no switches pressed
            CALL WAITSETUP
            CALL WAITSELECT
 
;-------------------------------------------------------------------------;
;      This loop checks for either pushbutton and acts  accordingly       ;
;-------------------------------------------------------------------------;
 
KEYCHKLOOP  BTFSS PORTB,START_PB       ; check for start pressed
            GOTO STARTCNT              ; yes, start count
            BTFSS PORTB,SET_PB         ; check for set pressed
            GOTO SETDISP               ; yes, set display
            BTFSS PORTA,SELECT_PB      ; check select pushbutton pressed
            GOTO SETSELECT             ; yes, select starting count
            GOTO KEYCHKLOOP            ; loop to catch key press
 
;-------------------------------------------------------------------------;
;    If start key has been pressed then start countdown process,          ;
;    I initially released this code with only the setting of the          ;
;    run flag included.  If you think about it you must also reset        ;
;    TMR0 to zero.  TMR0 is free running and could have any value         ;
;    0-255 when the button in pressed. Also INTCNT has to be              ;
;    initialized because the previous count could have been cancelled.    ;
;-------------------------------------------------------------------------;
 
STARTCNT    CALL WAITSTARTUP           ; wait for release of start key
            MOVLW D'244'               ; reset INTCNT
            MOVWF INTCNT
            CLRF TMR0                  ; and clear timer 0
            BSF RUNFLG, 0              ; start the countdown
 
;-------------------------------------------------------------------------;
;        Once started just loop looking for cancel or reaching 0000       ;
;-------------------------------------------------------------------------;
 
MAINLOOP    BTFSS PORTB,START_PB       ; countdown in progress, check start
            GOTO EE2D                  ; start over again if pressed
            BTFSC ALARM, 0             ; reached 0000 yet?
            GOTO SOUNDALARM            ; yes, turn alarm on
            GOTO MAINLOOP              ; no start switch, continue looping
 
;-------------------------------------------------------------------------;
;    This code sounds the alarm and waits on start to be pressed          ;
;-------------------------------------------------------------------------;
 
SOUNDALARM
FINALWAIT   BCF PORTB,RB4              ; speaker leads set up
            BSF PORTB,RB5              ; opposite polarity
            MOVLW 2                    ; delay 2 milliseconds
            CALL NMSEC
            BSF PORTB,RB4              ; flip the speaker leads
            BCF PORTB,RB5
            MOVLW 2                    ; another 2 msec delay
            CALL NMSEC
            BTFSC PORTB,START_PB       ; start button pressed
            GOTO  FINALWAIT            ; not yet
            CALL DLY20                 ; debounce just to make sure
            BTFSC PORTB,START_PB       ; second look
            GOTO FINALWAIT             ; nah, keep waiting
            BCF PORTB,RB4              ; speaker leads set to same polarity
            BCF PORTB,RB5
            CALL WAITSTARTUP           ; now wait for the switch up
            GOTO EE2D                  ; start all over again
 
;-------------------------------------------------------------------------;
;                    Wait for release of start button                     ;
;-------------------------------------------------------------------------;
 
WAITSTARTUP BTFSS PORTB,START_PB       ; wait for release
            GOTO WAITSTARTUP           ; not released yet
            CALL DLY20                 ; debounce release 
            BTFSS PORTB,START_PB       ; 2nd check, make sure released
            GOTO WAITSTARTUP           ; keep checking
            RETURN
 
;-------------------------------------------------------------------------;
;                    Wait for release of set button                       ;
;-------------------------------------------------------------------------;
 
WAITSETUP   BTFSS PORTB,SET_PB         ; wait for release
            GOTO WAITSETUP             ; not yet
            CALL DLY20                 ; debounce release 
            BTFSS PORTB,SET_PB         ; 2nd check, make sure released
            GOTO WAITSETUP             ; keep checking
            RETURN
 
;-------------------------------------------------------------------------;
;                    Wait for release of select button                    ;
;-------------------------------------------------------------------------;
 
WAITSELECT  BTFSS PORTA,SELECT_PB      ; wait for release
            GOTO WAITSELECT            ; not yet
            CALL DLY20                 ; debounce release 
            BTFSS PORTA,SELECT_PB      ; 2nd check, make sure released
            GOTO WAITSELECT            ; keep checking
            RETURN
 
;-------------------------------------------------------------------------;
;       Routine to follow sets the countdown time digit by digit          ;
;-------------------------------------------------------------------------;
 
SETDISP     CALL WAITSETUP             ; wait for set key to be released
            MOVLW H'0A'                ; put A's in digits, (no display)
            MOVWF MIN10                ; 10's of minutes
            MOVWF MIN                  ; minutes
            MOVWF SEC10                ; 10's of seconds
            MOVWF SEC                  ; seconds
STARTMIN10  CLRF  MIN10                ; 0 now in MIN10
MOREMIN10   MOVLW H'32'                ; 50 delays of 20 msec
            MOVWF SECNT                ; into counting register
WAIT1       CALL DLY20                 
            BTFSS PORTB,SET_PB         ; set key pressed?
            GOTO MINSET                ; yes MIN10 now set
            DECFSZ  SECNT,f            ; finished 1 sec delay?
            GOTO WAIT1                 ; continue wait
            INCF MIN10,f               ; every second increment 10's MIN
            MOVLW H'0A'                ; reached 10?
            SUBWF MIN10,W              
            BTFSC STATUS,Z             ; Z set if reached 10
            GOTO STARTMIN10            ; start again with 0
            GOTO MOREMIN10             ; set up another 1 sec delay
MINSET      CALL WAITSETUP             ; wait for release of set key
STARTMIN    CLRF MIN                   ; 0 into MIN
MOREMIN     MOVLW H'32'                ; 50 delays of 20 msec
            MOVWF SECNT                ; into counting register
WAIT2       CALL DLY20                 
            BTFSS PORTB,SET_PB         ; set pressed?
            GOTO SETSEC10              ; yes, finished with MIN
            DECFSZ SECNT,f             ; finished 1 sec delay?
            GOTO WAIT2                 ; continue wait
            INCF MIN,f                 ; every second increment MIN
            MOVLW H'0A'                ; reached 10?
            SUBWF MIN,W              
            BTFSC STATUS,Z             ; Z set if reached 10
            GOTO STARTMIN              ; put zero in if Z set
            GOTO MOREMIN               ; set up another 1 sec delay
SETSEC10    CALL WAITSETUP             ; wait release
STARTSEC10  CLRF SEC10                 ; 0 into SEC10
MORESEC10   MOVLW H'32'                ; 50 delays of 20 msec
            MOVWF SECNT                ; into counting register
WAIT3       CALL DLY20                 
            BTFSS PORTB,SET_PB         ; set pressed?
            GOTO  SETSEC               ; yes quit incrementing
            DECFSZ SECNT,f             ; finished 1 sec delay?
            GOTO WAIT3                 ; continue wait
            INCF SEC10,f               ; every second increment 10's SEC
            MOVLW H'06'                ; reached 6?
            SUBWF SEC10,W              
            BTFSC STATUS,Z             ; Z set if reached 6
            GOTO STARTSEC10            ; put zero in if Z set
            GOTO MORESEC10             ; set up another 1 sec delay
SETSEC      CALL WAITSETUP             ; wait for release
STARTSEC    CLRF SEC                   ; 0 into SEC
MORESEC     MOVLW H'32'                ; 50 delays of 20 msec
            MOVWF SECNT                ; into counting register
WAIT4       CALL DLY20                 
            BTFSS PORTB,SET_PB         ; set button pressed?
            GOTO  FINSET               ; yes finished setting digits
            DECFSZ SECNT,f             ; finished 1 sec delay?
            GOTO WAIT4                 ; continue wait
            INCF SEC,f                 ; every second increment SEC
            MOVLW H'0A'                ; reached 10?
            SUBWF SEC,W              
            BTFSC STATUS,Z             ; Z set if reached 10
            GOTO STARTSEC              ; put zero in if Z set
            GOTO MORESEC               ; set up another 1 sec delay
FINSET      BCF INTCON, GIE            ; disable interrupts
            CALL PUTEE                 ; put new digits into EEPROM
            BSF INTCON, GIE            ; re-enable interrupts
            CALL WAITSETUP             ; make sure set switch up
            GOTO KEYCHKLOOP            ; start checking buttons again
 
;-------------------------------------------------------------------------;
;        Selects starting count by changing EEPROM location 0             ;
;-------------------------------------------------------------------------;
 
SETSELECT   MOVLW D'4'                 ; offset up 4
            ADDWF OFFSET,F             ; next offset position
            MOVLW D'60'                ; reached 16th yet?
            SUBWF OFFSET,W             ; will give zero if yes
            BTFSC STATUS,Z             ; skip if not 64
            CLRF  OFFSET               ; reset position to zero
            MOVLW 0                    ; EEPROM location
            MOVWF EEADR                ; set up address
            MOVF OFFSET,W              ; offset # into W
            MOVWF EEDATA               ; set up data
            BCF INTCON,GIE             ;  clear GIE, disable interrupts
            CALL WRITEEE               ; save # in location 0
            BSF INTCON,GIE             ; re-enable interrupts
            CALL GETEE                 ; get new start count into display
            CALL WAITSELECT            ; make sure select switch is up
            GOTO KEYCHKLOOP            ; start checking buttons again
 
;-------------------------------------------------------------------------;
;  The following are various delay routines based on instruction length.  ;  
;  The instruction length is assumed to be 1 microsecond (4Mhz crystal).  ;
;-------------------------------------------------------------------------;
 
DLY20       MOVLW 20                   ; delay for 20 milliseconds
                ;*** N millisecond delay routine ***
NMSEC       MOVWF CNTMSEC              ; delay for N (in W) milliseconds
MSECLOOP    MOVLW D'248'               ; load takes 1 microsec
            CALL MICRO4                ; by itself CALL takes ...
                                       ; 2 + 247 X 4 + 3 + 2 = 995
            NOP                        ; 1 more microsec 
            DECFSZ CNTMSEC,f           ; 1 when skip not taken, else 2
            GOTO MSECLOOP              ; 2 here: total 1000 per msecloop
            RETURN                     ; final time through takes 999 to here
                                       ; overhead in and out ignored
 
                ;***  1 millisecond delay routine ***
ONEMSEC     MOVLW D'249'               ; 1 microsec for load W
                                       ; loops below take 248 X 4 + 3 = 995
MICRO4      ADDLW H'FF'                ; subtract 1 from 'W'
            BTFSS STATUS,Z             ; skip when you reach zero
            GOTO MICRO4                ; loops takes 4 microsec, 3 for last
            RETURN                     ; takes 2 microsec
                                       ; call + load  W + loops + return =
                                       ; 2 + 1 + 995 + 2 = 1000 microsec
 
;-------------------------------------------------------------------------;
;    Here we set up the initial values of the digits in data EEPROM       ;
;-------------------------------------------------------------------------;
           ORG H'2100'
 
          DE 0, 1, 0, 0, 0    ; 1st starting #
          DE  2, 0, 0, 0      ; 2nd starting #
          DE  3, 0, 0, 0      ; 3rd starting #
          DE  4, 0, 0, 0      ; 4th starting #
          DE  5, 0, 0, 0      ; 5th starting #
          DE  6, 0, 0, 0      ; 6th starting #
          DE  7, 0, 0, 0      ; 7th starting #
          DE  8, 0, 0, 0      ; 8th starting #
          DE  9, 0, 0, 0      ; 9th starting #
          DE  0, 1, 0, 0      ; 10th starting #
          DE  1, 1, 0, 0      ; 11th starting #
          DE  2, 1, 0, 0      ; 12th starting #
          DE  3, 1, 0, 0      ; 13th starting #
          DE  4, 1, 0, 0      ; 14th starting #
          DE  5, 1, 0, 0      ; 15th starting #
 
            END

Picproje Elektronik Sitesi

Haberler:

PIC ile darkroom timer

ilker_32

	;-------------------------------------------------------------------------;
	; Darkroom Timer ;
	; April '99 Stan Ockers (ockers@anl.gov) ;
	; circuit diagram in CNTDN.PCX ;
	; further description in CNTDN.TXT ;
	; ;
	; Counts down from 0-99 min and 0-59 sec giving an alarm at 0 ;
	; initial counts are held in data EEPROM setable with one button ;
	; ;
	; RBO-RB3 to bases of transistors connect to common cathode of displays. ;
	; RA0-RA3 to 1,2,4,8 BCD inputs of CD4511 7 segment latch and driver. ;
	; RB7 to start pushbutton used to start countdown and silence alarm. ;
	; RB6 goes to time set pushbutton use to sucessively set the digits. ;
	; RA4 with pull-up resistor goes to PB to select from 15 starting counts ;
	; RB4 and RB5 go to speaker which gives an alarm. ;
	;-------------------------------------------------------------------------;


	LIST P=16F84
	#INCLUDE "p16f84.inc"

	;-------------------------------------------------------------------------;
	; Here we define our own personal registers and give them names ;
	;-------------------------------------------------------------------------;

	SEC EQU H'0C' ; this register holds the value of seconds
	SEC10 EQU H'0D' ; holds value of 10's of seconds
	MIN EQU H'0E' ; holds value of minutes
	MIN10 EQU H'0F' ; holds value of 10's of minutes
	DIGCTR EQU H'10' ; 8 bit counter, only 2 lowest bits actually used
	DIGIT EQU H'11' ; hold digit number to access table
	INTCNT EQU H'12' ; counts # interrupts to determine when 1 sec up
	FUDGE EQU H'13' ; allows slight adjustment every 7 interrupts
	RUNFLG EQU H'14' ; bit 0 only, tells if countdown in progress
	W_TEMP EQU H'15' ; temporarily holds value of W
	STATUS_TEMP EQU H'16' ; temporarily holds value of STATUS
	SECNT EQU H'17' ; used in counting 50, 20 msec delays for 1 sec
	CNTMSEC EQU H'18' ; used in timing of milliseconds
	ALARM EQU H'19' ; bit 0 only, used as flag for when to alarm
	OFFSET EQU H'1A' ; hold offset of address in EEPROM

	;-------------------------------------------------------------------------;
	; Here we give names to some numbers to make their use more clear ;
	;-------------------------------------------------------------------------;

	#DEFINE START_PB D'7'
	#DEFINE SET_PB D'6'
	#DEFINE SELECT_PB D'4'
	#DEFINE RB4 D'4'
	#DEFINE RB5 D'5'


	;-------------------------------------------------------------------------;
	; We set the start of code to orginate a location zero ;
	;-------------------------------------------------------------------------;

	ORG 0

	GOTO MAIN ; jump to the main routine
	NOP
	NOP
	NOP
	GOTO INTERRUPT ; interrupt routine

	;-------------------------------------------------------------------------;
	; This table is used to get a bit pattern that will turn on a digit ;
	;-------------------------------------------------------------------------;

	BITPAT ADDWF PCL,f ; get bit pattern for transistors
	RETLW H'0E' ; a low, (0), turns the transistor on
	RETLW H'0D'
	RETLW H'0B'
	RETLW H'07'

	;-------------------------------------------------------------------------;
	; Initialization routine sets up ports and timer ;
	;-------------------------------------------------------------------------;

	INIT MOVLW H'C0' ; PB6 & PB7 inputs all others outputs
	TRIS PORTB
	MOVLW H'10' ; Port RA4 input, others outputs
	TRIS PORTA
	MOVLW H'03' ; prescaler on TMR0 and 1:16
	OPTION
	MOVLW H'A0' ; GIE & T0IE set T0IF cleared
	MOVWF INTCON
	MOVLW H'F4' ; initialize INTCNT
	MOVWF INTCNT
	MOVLW H'06' ; initialize FUDGE
	MOVWF FUDGE
	CLRF OFFSET ; initialize OFFSET
	RETURN

	;-------------------------------------------------------------------------;
	; This is the interrupt routine that is jumped to when TMR0 overflows ;
	;-------------------------------------------------------------------------;

	INTERRUPT MOVWF W_TEMP ; save W
	SWAPF STATUS,W ; save status
	MOVWF STATUS_TEMP ; without changing flags
	INCF DIGCTR,f ; next digit #
	MOVF DIGCTR,W ; get it into W
	ANDLW H'03' ; mask off 2 lowest bits
	MOVWF DIGIT ; save it for later
	ADDLW H'0C' ; point at register to display
	MOVWF FSR ; use as pointer
	MOVF INDF,W ; get value of reg pointed to into W
	MOVWF PORTA ; output to CD4511
	MOVF DIGIT,W ; recall digit #
	CALL BITPAT ; get bit pattern
	MOVWF PORTB ; select transistor
	DECFSZ INTCNT,f ; finished 1 sec ?
	GOTO RESTORE ; not yet, return and enable inter.
	CALL EVERYSEC ; go to every second routine
	MOVLW H'F4' ; reset INTCNT to normal value
	MOVWF INTCNT
	DECFSZ FUDGE,f ; time for fudge?
	GOTO RESTORE ; not yet, continue on
	MOVLW H'06' ; reset FUDGE to 6
	MOVWF FUDGE
	INCF INTCNT,f ; INTCNT to 245
	RESTORE SWAPF STATUS_TEMP,W ; get original status back
	MOVWF STATUS ; into status register
	SWAPF STATUS_TEMP,f ; old no flags trick again
	SWAPF STATUS_TEMP,W ; to restore W
	BCF INTCON,T0IF ; clear the TMR0 interrupt flag
	RETFIE ; finished

	;-------------------------------------------------------------------------;
	; This routine is called by the interrupt routine every second ;
	;-------------------------------------------------------------------------;

	EVERYSEC BTFSS RUNFLG,0 ; return if runflg not set
	RETURN
	DECF SEC,f ; decrement seconds digit
	INCFSZ SEC,W ; test for underflow
	GOTO CKZERO
	MOVLW H'09' ; reset sec to 9
	MOVWF SEC
	DECF SEC10,f ; decrement SEC10
	INCFSZ SEC10,W ; check underflow
	GOTO CKZERO
	MOVLW H'05'
	MOVWF SEC10
	DECF MIN,f
	INCFSZ MIN,W
	GOTO CKZERO
	MOVLW H'09'
	MOVWF MIN
	DECF MIN10,f
	CKZERO MOVF SEC,f ; test SEC for zero
	BTFSS STATUS,Z
	RETURN
	MOVF SEC10,f ; check SEC10 for zero
	BTFSS STATUS,Z
	RETURN
	MOVF MIN,f ; check MIN for zero
	BTFSS STATUS,Z
	RETURN
	MOVF MIN10,f ; check MIN10 for zero
	BTFSS STATUS,Z
	RETURN
	CLRF RUNFLG ; stop the countdown
	BSF ALARM, 0 ; set the alarm flag
	RETURN

	;-------------------------------------------------------------------------;
	; This is a routine to read a byte from the data EEPROM ;
	;-------------------------------------------------------------------------;

	READEE MOVWF EEADR ; set up eeprom address from W
	BSF STATUS,RP0 ; change to page 1
	BSF EECON1,RD ; set the read bit
	BCF STATUS,RP0 ; back to page 0
	MOVF EEDATA,W ; return value in W
	RETURN

	;-------------------------------------------------------------------------;
	; This routine fills the display registers from data EEPROM ;
	;-------------------------------------------------------------------------;

	GETEE MOVLW H'01' ; EEprom location 1 +
	ADDWF OFFSET,W ; offset from start
	CALL READEE ; into W
	MOVWF SEC ; into SEC register
	MOVLW H'02' ; location 2 +
	ADDWF OFFSET,W ; offset from start
	CALL READEE ; into W
	MOVWF SEC10 ; into SEC10 register
	MOVLW H'03' ; location 3 +
	ADDWF OFFSET,W ; offset from start
	CALL READEE ; into W
	MOVWF MIN ; into MIN register
	MOVLW H'04' ; location 4 +
	ADDWF OFFSET,W ; offset from start
	CALL READEE ; into W
	MOVWF MIN10 ; into MIN10 register
	RETURN

	;-------------------------------------------------------------------------;
	; This routine writes a byte to data EEPROM ;
	;-------------------------------------------------------------------------;

	WRITEEE BSF STATUS,RP0 ; set up EEADR and EEDATA first
	CLRF EECON1
	BSF EECON1,WREN ; enable write
	MOVLW H'55' ; magic sequence
	MOVWF EECON2
	MOVLW H'AA'
	MOVWF EECON2
	BSF EECON1,WR
	EELOOP BTFSC EECON1,WR ; wait for WR to go low
	GOTO EELOOP ; not yet
	BSF EECON1,WREN
	BCF EECON1,EEIF ; clear the interrupt flag
	BCF STATUS,RP0 ; return to page 0
	RETURN

	;-------------------------------------------------------------------------;
	; This routine puts display registers into data EEPROM ;
	;-------------------------------------------------------------------------;

	PUTEE MOVF SEC,W ; put digit registers into EEprom
	MOVWF EEDATA
	MOVLW H'01' ; EEPROM location 1 +
	ADDWF OFFSET,W ; offset from start
	MOVWF EEADR
	CALL WRITEEE
	MOVF SEC10,W
	MOVWF EEDATA
	MOVLW H'02' ; EEPROM location 2 +
	ADDWF OFFSET,W ; offset from start
	MOVWF EEADR
	CALL WRITEEE
	MOVF MIN,W
	MOVWF EEDATA
	MOVLW H'03' ; EEPROM location 3 +
	ADDWF OFFSET,W ; offset from start
	MOVWF EEADR
	CALL WRITEEE
	MOVF MIN10,W
	MOVWF EEDATA
	MOVLW H'04' ; EEPROM location 4 +
	ADDWF OFFSET,W ; offset from start
	MOVWF EEADR
	CALL WRITEEE
	RETURN

	;-------------------------------------------------------------------------;
	; This is the main routine, the program starts here ;
	;-------------------------------------------------------------------------;

	MAIN CALL INIT ; set up ports etc.

	;-------------------------------------------------------------------------;
	; We will return to this point when alarm is shut off. ;
	;-------------------------------------------------------------------------;

	EE2D CALL GETEE ; put eeprom in display regs.
	BCF RUNFLG, 0 ; clear run flag so no countdown
	BCF ALARM, 0 ; clear alarm flag
	CALL WAITSTARTUP ; wait till no switches pressed
	CALL WAITSETUP
	CALL WAITSELECT

	;-------------------------------------------------------------------------;
	; This loop checks for either pushbutton and acts accordingly ;
	;-------------------------------------------------------------------------;

	KEYCHKLOOP BTFSS PORTB,START_PB ; check for start pressed
	GOTO STARTCNT ; yes, start count
	BTFSS PORTB,SET_PB ; check for set pressed
	GOTO SETDISP ; yes, set display
	BTFSS PORTA,SELECT_PB ; check select pushbutton pressed
	GOTO SETSELECT ; yes, select starting count
	GOTO KEYCHKLOOP ; loop to catch key press

	;-------------------------------------------------------------------------;
	; If start key has been pressed then start countdown process, ;
	; I initially released this code with only the setting of the ;
	; run flag included. If you think about it you must also reset ;
	; TMR0 to zero. TMR0 is free running and could have any value ;
	; 0-255 when the button in pressed. Also INTCNT has to be ;
	; initialized because the previous count could have been cancelled. ;
	;-------------------------------------------------------------------------;

	STARTCNT CALL WAITSTARTUP ; wait for release of start key
	MOVLW D'244' ; reset INTCNT
	MOVWF INTCNT
	CLRF TMR0 ; and clear timer 0
	BSF RUNFLG, 0 ; start the countdown

	;-------------------------------------------------------------------------;
	; Once started just loop looking for cancel or reaching 0000 ;
	;-------------------------------------------------------------------------;

	MAINLOOP BTFSS PORTB,START_PB ; countdown in progress, check start
	GOTO EE2D ; start over again if pressed
	BTFSC ALARM, 0 ; reached 0000 yet?
	GOTO SOUNDALARM ; yes, turn alarm on
	GOTO MAINLOOP ; no start switch, continue looping

	;-------------------------------------------------------------------------;
	; This code sounds the alarm and waits on start to be pressed ;
	;-------------------------------------------------------------------------;

	SOUNDALARM
	FINALWAIT BCF PORTB,RB4 ; speaker leads set up
	BSF PORTB,RB5 ; opposite polarity
	MOVLW 2 ; delay 2 milliseconds
	CALL NMSEC
	BSF PORTB,RB4 ; flip the speaker leads
	BCF PORTB,RB5
	MOVLW 2 ; another 2 msec delay
	CALL NMSEC
	BTFSC PORTB,START_PB ; start button pressed
	GOTO FINALWAIT ; not yet
	CALL DLY20 ; debounce just to make sure
	BTFSC PORTB,START_PB ; second look
	GOTO FINALWAIT ; nah, keep waiting
	BCF PORTB,RB4 ; speaker leads set to same polarity
	BCF PORTB,RB5
	CALL WAITSTARTUP ; now wait for the switch up
	GOTO EE2D ; start all over again

	;-------------------------------------------------------------------------;
	; Wait for release of start button ;
	;-------------------------------------------------------------------------;

	WAITSTARTUP BTFSS PORTB,START_PB ; wait for release
	GOTO WAITSTARTUP ; not released yet
	CALL DLY20 ; debounce release
	BTFSS PORTB,START_PB ; 2nd check, make sure released
	GOTO WAITSTARTUP ; keep checking
	RETURN

	;-------------------------------------------------------------------------;
	; Wait for release of set button ;
	;-------------------------------------------------------------------------;

	WAITSETUP BTFSS PORTB,SET_PB ; wait for release
	GOTO WAITSETUP ; not yet
	CALL DLY20 ; debounce release
	BTFSS PORTB,SET_PB ; 2nd check, make sure released
	GOTO WAITSETUP ; keep checking
	RETURN

	;-------------------------------------------------------------------------;
	; Wait for release of select button ;
	;-------------------------------------------------------------------------;

	WAITSELECT BTFSS PORTA,SELECT_PB ; wait for release
	GOTO WAITSELECT ; not yet
	CALL DLY20 ; debounce release
	BTFSS PORTA,SELECT_PB ; 2nd check, make sure released
	GOTO WAITSELECT ; keep checking
	RETURN

	;-------------------------------------------------------------------------;
	; Routine to follow sets the countdown time digit by digit ;
	;-------------------------------------------------------------------------;

	SETDISP CALL WAITSETUP ; wait for set key to be released
	MOVLW H'0A' ; put A's in digits, (no display)
	MOVWF MIN10 ; 10's of minutes
	MOVWF MIN ; minutes
	MOVWF SEC10 ; 10's of seconds
	MOVWF SEC ; seconds
	STARTMIN10 CLRF MIN10 ; 0 now in MIN10
	MOREMIN10 MOVLW H'32' ; 50 delays of 20 msec
	MOVWF SECNT ; into counting register
	WAIT1 CALL DLY20
	BTFSS PORTB,SET_PB ; set key pressed?
	GOTO MINSET ; yes MIN10 now set
	DECFSZ SECNT,f ; finished 1 sec delay?
	GOTO WAIT1 ; continue wait
	INCF MIN10,f ; every second increment 10's MIN
	MOVLW H'0A' ; reached 10?
	SUBWF MIN10,W
	BTFSC STATUS,Z ; Z set if reached 10
	GOTO STARTMIN10 ; start again with 0
	GOTO MOREMIN10 ; set up another 1 sec delay
	MINSET CALL WAITSETUP ; wait for release of set key
	STARTMIN CLRF MIN ; 0 into MIN
	MOREMIN MOVLW H'32' ; 50 delays of 20 msec
	MOVWF SECNT ; into counting register
	WAIT2 CALL DLY20
	BTFSS PORTB,SET_PB ; set pressed?
	GOTO SETSEC10 ; yes, finished with MIN
	DECFSZ SECNT,f ; finished 1 sec delay?
	GOTO WAIT2 ; continue wait
	INCF MIN,f ; every second increment MIN
	MOVLW H'0A' ; reached 10?
	SUBWF MIN,W
	BTFSC STATUS,Z ; Z set if reached 10
	GOTO STARTMIN ; put zero in if Z set
	GOTO MOREMIN ; set up another 1 sec delay
	SETSEC10 CALL WAITSETUP ; wait release
	STARTSEC10 CLRF SEC10 ; 0 into SEC10
	MORESEC10 MOVLW H'32' ; 50 delays of 20 msec
	MOVWF SECNT ; into counting register
	WAIT3 CALL DLY20
	BTFSS PORTB,SET_PB ; set pressed?
	GOTO SETSEC ; yes quit incrementing
	DECFSZ SECNT,f ; finished 1 sec delay?
	GOTO WAIT3 ; continue wait
	INCF SEC10,f ; every second increment 10's SEC
	MOVLW H'06' ; reached 6?
	SUBWF SEC10,W
	BTFSC STATUS,Z ; Z set if reached 6
	GOTO STARTSEC10 ; put zero in if Z set
	GOTO MORESEC10 ; set up another 1 sec delay
	SETSEC CALL WAITSETUP ; wait for release
	STARTSEC CLRF SEC ; 0 into SEC
	MORESEC MOVLW H'32' ; 50 delays of 20 msec
	MOVWF SECNT ; into counting register
	WAIT4 CALL DLY20
	BTFSS PORTB,SET_PB ; set button pressed?
	GOTO FINSET ; yes finished setting digits
	DECFSZ SECNT,f ; finished 1 sec delay?
	GOTO WAIT4 ; continue wait
	INCF SEC,f ; every second increment SEC
	MOVLW H'0A' ; reached 10?
	SUBWF SEC,W
	BTFSC STATUS,Z ; Z set if reached 10
	GOTO STARTSEC ; put zero in if Z set
	GOTO MORESEC ; set up another 1 sec delay
	FINSET BCF INTCON, GIE ; disable interrupts
	CALL PUTEE ; put new digits into EEPROM
	BSF INTCON, GIE ; re-enable interrupts
	CALL WAITSETUP ; make sure set switch up
	GOTO KEYCHKLOOP ; start checking buttons again

	;-------------------------------------------------------------------------;
	; Selects starting count by changing EEPROM location 0 ;
	;-------------------------------------------------------------------------;

	SETSELECT MOVLW D'4' ; offset up 4
	ADDWF OFFSET,F ; next offset position
	MOVLW D'60' ; reached 16th yet?
	SUBWF OFFSET,W ; will give zero if yes
	BTFSC STATUS,Z ; skip if not 64
	CLRF OFFSET ; reset position to zero
	MOVLW 0 ; EEPROM location
	MOVWF EEADR ; set up address
	MOVF OFFSET,W ; offset # into W
	MOVWF EEDATA ; set up data
	BCF INTCON,GIE ; clear GIE, disable interrupts
	CALL WRITEEE ; save # in location 0
	BSF INTCON,GIE ; re-enable interrupts
	CALL GETEE ; get new start count into display
	CALL WAITSELECT ; make sure select switch is up
	GOTO KEYCHKLOOP ; start checking buttons again

	;-------------------------------------------------------------------------;
	; The following are various delay routines based on instruction length. ;
	; The instruction length is assumed to be 1 microsecond (4Mhz crystal). ;
	;-------------------------------------------------------------------------;

	DLY20 MOVLW 20 ; delay for 20 milliseconds
	;* N millisecond delay routine *
	NMSEC MOVWF CNTMSEC ; delay for N (in W) milliseconds
	MSECLOOP MOVLW D'248' ; load takes 1 microsec
	CALL MICRO4 ; by itself CALL takes ...
	; 2 + 247 X 4 + 3 + 2 = 995
	NOP ; 1 more microsec
	DECFSZ CNTMSEC,f ; 1 when skip not taken, else 2
	GOTO MSECLOOP ; 2 here: total 1000 per msecloop
	RETURN ; final time through takes 999 to here
	; overhead in and out ignored

	;* 1 millisecond delay routine *
	ONEMSEC MOVLW D'249' ; 1 microsec for load W
	; loops below take 248 X 4 + 3 = 995
	MICRO4 ADDLW H'FF' ; subtract 1 from 'W'
	BTFSS STATUS,Z ; skip when you reach zero
	GOTO MICRO4 ; loops takes 4 microsec, 3 for last
	RETURN ; takes 2 microsec
	; call + load W + loops + return =
	; 2 + 1 + 995 + 2 = 1000 microsec

	;-------------------------------------------------------------------------;
	; Here we set up the initial values of the digits in data EEPROM ;
	;-------------------------------------------------------------------------;
	ORG H'2100'

	DE 0, 1, 0, 0, 0 ; 1st starting #
	DE 2, 0, 0, 0 ; 2nd starting #
	DE 3, 0, 0, 0 ; 3rd starting #
	DE 4, 0, 0, 0 ; 4th starting #
	DE 5, 0, 0, 0 ; 5th starting #
	DE 6, 0, 0, 0 ; 6th starting #
	DE 7, 0, 0, 0 ; 7th starting #
	DE 8, 0, 0, 0 ; 8th starting #
	DE 9, 0, 0, 0 ; 9th starting #
	DE 0, 1, 0, 0 ; 10th starting #
	DE 1, 1, 0, 0 ; 11th starting #
	DE 2, 1, 0, 0 ; 12th starting #
	DE 3, 1, 0, 0 ; 13th starting #
	DE 4, 1, 0, 0 ; 14th starting #
	DE 5, 1, 0, 0 ; 15th starting #

	END