Microchip Davidtait Clock.txt
; **************************************************************************
;
; 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: 2025/1/13 04:28,
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