; ************************************************************************** ; ; CLOCK.ASM ; ; Displays time on a single 7-segment display. The timing source ; can be an NTSC colour burst crystal (3.579454 MHz) or a 4 MHz ; crystal. ; ; A common anode 7-segment LED display is attached as follows: ; ; RA0 segment a ; RA1 segment b ; RA2 segment c ; RA3 segment d ; RA4 segment e ; RB4 segment f ; RB5 segment g ; ; Each segment is connected via a 470 ohm resistor. The common anode ; is connected directly to VDD. The strange allocation of port bits ; to segments allows RB6 and RB7 to be dedicated to in-circuit serial ; programming. ; ; The time is displayed digit by digit over a four second period ; every 15 seconds and the display is blank otherwise. Four LEDs are ; connected from RB3-RB0 to GND via 470 ohm resistors; these are used ; to indicate the significance of the displayed digit: 10s of hours - ; hours - 10s of minutes - minutes. ; ; A normally open switch is connected from RB7 to GND via a 470 ohm ; resistor; no pull-up resistor is needed as an internal weak pull-up ; is enabled by the program. To set the clock press the switch when ; the appropriate digit is displayed; the digit can then be incremented ; by pressing the switch repeatedly. If the switch is open for about ; 2 seconds the clock display is restarted allowing another digit to be ; changed. It is up to the user to put in sensible times as no checking ; is done by the program. ; ; To permit the PIC to be programmed in-circuit the /MCLR pin is ; connected to VDD via a 1k resistor in series with a signal diode ; (e.g. 1N4148) with anode connected to VDD. ; ; ; Copyright (C) 1998 David Tait (david.tait@man.ac.uk) ; ;************************************************************************** LIST P=16F84 ; no need to change this for the 16C84 ERRORLEVEL -302 ; suppress bank selection messages __CONFIG 3FF9H ; XT oscillator (and PWRTE if 16C84) #DEFINE _3_58MHZ ; choose clock speed ;#DEFINE _4_00MHZ PCL EQU 2 ; registers are defined here to make this STATUS EQU 3 ; program self contained. PORTA EQU 5 PORTB EQU 6 INTCON EQU 0BH TRISA EQU 85H TRISB EQU 86H OPTREG EQU 81H C EQU 0 ; bits in STATUS Z EQU 2 RP0 EQU 5 T0IF EQU 2 ; bit in INTCON #IFDEF _3_58MHZ ; number of ticks per second for 3.58 MHz: TCK0 EQU .109 ; nominal TCK1 EQU .111 ; every 10 secs TCK2 EQU .113 ; every min TCK3 EQU .115 ; every 10 mins TCK4 EQU .114 ; every hour TCK5 EQU .110 ; every 10 hours TCK6 EQU .111 ; every 24 hours #ENDIF #IFDEF _4_00MHZ ; as above but for 4 MHz TCK0 EQU .122 TCK1 EQU .123 TCK2 EQU .121 TCK3 EQU .123 TCK4 EQU .124 TCK5 EQU .125 TCK6 EQU .125 #ENDIF CBLOCK 0CH ; define variables required TICKS ; decremented every tick (9.15 ms or 8.19 ms) SEGS ; one bit per segment: "-gfedcba" SEC SEC10 MIN MIN10 HOUR HOUR10 FRAME ; used to decide when to display time HHMM ; one bit per digit displayed COUNT ; scratch register DIGIT ; last digit displayed ENDC ;*********************************; ; Initialisation ; ;*********************************; ORG 0 INIT CLRF SEC CLRF SEC10 CLRF MIN CLRF MIN10 CLRF HOUR CLRF HOUR10 CLRF FRAME CLRF PORTA CLRF PORTB BSF STATUS,RP0 ; select register bank 1 CLRF TRISA MOVLW 80H MOVWF TRISB ; only RB7 is an input MOVLW 4 MOVWF OPTREG ; assign prescaler (1:32) to TMR0 BCF STATUS,RP0 ; reselect bank 0 ;*********************************; ; Main Program ; ;*********************************; MAIN CALL CLOCK ; real-time clock algo called every second CALL SHOW ; display the time WAIT BTFSS INTCON,T0IF ; wait for TMR0 to roll over GOTO WAIT CLRF INTCON CALL CHKSW ; check for button press DECFSZ TICKS,F GOTO WAIT GOTO MAIN ; get here every second ;*********************************; ; Convert digit to segment form ; ;*********************************; SEGTAB ANDLW 0FH ADDWF PCL,F DT 40,79,24,30,19,12,02,78,00,10 DT 7F,7F,7F,7F,7F,7F ;*********************************; ; Real-time clock algorithm ; ;*********************************; CLOCK MOVLW TCK0 ; increment digits as appropriate MOVWF TICKS ; and define number of ticks per INCF SEC,F ; second for next second MOVF SEC,W SUBLW 9 BTFSC STATUS,C RETURN MOVLW TCK1 MOVWF TICKS CLRF SEC INCF SEC10,F MOVF SEC10,W SUBLW 5 BTFSC STATUS,C RETURN MOVLW TCK2 MOVWF TICKS CLRF SEC10 INCF MIN,F MOVF MIN,W SUBLW 9 BTFSC STATUS,C RETURN MOVLW TCK3 MOVWF TICKS CLRF MIN INCF MIN10,F MOVF MIN10,W SUBLW 5 BTFSC STATUS,C RETURN MOVLW TCK4 MOVWF TICKS CLRF MIN10 MOVF HOUR10,W SUBLW 1 BTFSC STATUS,C GOTO INCHR INCF HOUR,F MOVF HOUR,W SUBLW 3 BTFSC STATUS,C RETURN MOVLW TCK6 MOVWF TICKS CLRF HOUR CLRF HOUR10 RETURN INCHR INCF HOUR,F MOVF HOUR,W SUBLW 9 BTFSC STATUS,C RETURN MOVLW TCK5 MOVWF TICKS CLRF HOUR INCF HOUR10,F RETURN ;*********************************; ; Displays the time digit by digit; ;*********************************; SHOW CLRF HHMM INCF FRAME,F ; increment place in frame MOVF FRAME,W SUBLW D'14' BTFSS STATUS,C CLRF FRAME MOVF FRAME,W XORLW 1 BTFSC STATUS,Z GOTO DHOUR10 ; display 10s of hours when frame is 1 XORLW 1^2 BTFSC STATUS,Z GOTO DHOUR ; display hour when frame is 2 XORLW 2^3 BTFSC STATUS,Z GOTO DMIN10 ; display 10s of mins when frame is 3 XORLW 3^4 BTFSC STATUS,Z GOTO DMIN ; display mins when frame is 4 MOVLW 30 ; otherwise blank display MOVWF PORTB MOVLW 1F MOVWF PORTA RETURN DHOUR10 BSF HHMM,3 MOVF HOUR10,W GOTO DISPLAY DHOUR BSF HHMM,2 MOVF HOUR,W GOTO DISPLAY DMIN10 BSF HHMM,1 MOVF MIN10,W GOTO DISPLAY DMIN BSF HHMM,0 MOVF MIN,W ; falls through to DISPLAY ;*********************************; ; Displays digit in W ; ;*********************************; DISPLAY MOVWF DIGIT ; save number to be displayed in DIGIT CALL SEGTAB ; convert to segment form MOVWF SEGS ; and store ANDLW 1FH ; extract PORTA segments MOVWF PORTA ; and display RRF SEGS,W ANDLW 30H ; extract PORTB segments IORWF HHMM,W MOVWF PORTB ; and display RETURN ;*********************************; ; Checks for a switch press and ; ; updates digit if displayed ; ;*********************************; CHKSW BTFSC PORTB,7 ; switch closed? RETURN ; no MOVF HHMM,F BTFSC STATUS,Z ; digit displayed? RETURN ; no INCDIG INCF DIGIT,F ; DIGIT is the currently displayed number MOVF DIGIT,W SUBLW 9 BTFSS STATUS,C CLRF DIGIT MOVF DIGIT,W CALL DISPLAY CALL DELAY ; wait for switch to settle CHKSW0 BTFSS PORTB,7 ; switch open? GOTO CHKSW0 ; no CALL DELAY BTFSS PORTB,7 ; still open? GOTO CHKSW0 ; no MOVLW D'20' MOVWF COUNT CHKSW1 BTFSS PORTB,7 ; switch open? GOTO INCDIG ; no CALL DELAY DECFSZ COUNT,F GOTO CHKSW1 MOVF DIGIT,W ; switch was open for around 2 secs CLRF FRAME CLRF SEC10 CLRF SEC BTFSC HHMM,3 ; update correct digit MOVWF HOUR10 BTFSC HHMM,2 MOVWF HOUR BTFSC HHMM,1 MOVWF MIN10 BTFSC HHMM,0 MOVWF MIN GOTO MAIN ; restart the program ;*********************************; ; Delay used by switch routine ; ;*********************************; DELAY MOVLW D'12' ; roughly 100ms delay MOVWF TICKS DEL1 BTFSS INTCON,T0IF ; wait for TMR0 to roll over GOTO DEL1 CLRF INTCON DECFSZ TICKS,F GOTO DEL1 RETURN END
| file: /Techref/microchip/davidtait/clock.txt, 8KB, , updated: 1998/5/27 02:00, local time: 2024/11/29 14:15,
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