NAM D2CLCK
*      THIS IS A 12 OR 24 HOUR CLOCK.
*      INITIAL SETUP: SET TIME IN HOUR,MINUTES,
*        AND SECONDS LOCATIONS. IF 24 HOUR
*        CLOCK IS DESIRED INSTEAD OF 12,
*        NOTE 2 CHANGES MARKED BY ASTERISKS.
*      ENTER: 0000G
*      DISPLAY:  HHMM SS
*      HARDWARE: MEK6800D2 KIT WITH 60 HZ CLOCK INPUT
*        TO PIA.  USE 10K RESISTOR FROM PIA (U20) PINS
*        17 AND 18 TO +5V.  USE SILICON DIODE FROM PIA
*        PINS 17 & 18 TO 60 HZ. A.C. (ANODE TO PIA).
PIADB  EQU $8006
PIACB  EQU $8007
INTLOC EQU $A000
OUTDS  EQU $E0FE
MISD01 EQU $E275
REGST5 EQU $E31C
REGST6 EQU $E327
INTRPT EQU $0019
SETDSP EQU $0051
CKDEC  EQU $0061
INTR1  EQU $001F
INTR2  EQU $0020
       SPC 1
START  NOP
       SEI
       CLRA SET UP PIA
       STAA ONE60
       STAA PIACB
       LDX #$00FF
       STX PIADB
       LDX #INTRPT
       STX INTLOC
       NOP
       CLI
       JMP OUTDS
       SPC 1
       CLRB
       LDAA PIADB READ
       BMI INTR2 IS A VALID INT?
       RTI NO
       SPC 1
       INC ONE60
       LDAA ONE60
       CMPA #60
       BNE INTR1
       STAB ONE60
       LDAA SECOND
       BSR CKDEC
       STAA SECOND
       CMPA #$60 SECONDS FULL?
       BNE SETDSP
       STAB SECOND YES
       LDAA MINUTE
       BSR CKDEC
       STAA MINUTE
       CMPA #$60
       BNE SETDSP MINUTES FULL?
       STAB MINUTE YES
       LDAA HOUR
       BSR CKDEC
       STAA HOUR
       CMPA #$13 ***MILITARY: CMP A #$24
       BNE SETDSP
       LDAA #01 ***MILITARY: LDA A #00
       STAA HOUR
       LDAA SECOND
       JSR MISD01
       LDAA MINUTE
       JSR REGST6
       LDAA HOUR
       JSR REGST5
       RTI
       SPC 1
       ADD A #01
       DAA
       RTS
       SPC 1
       ORG $0065
HOUR   FCB 00
MINUTE FCB 00
SECOND FCB 00
ONE60  FCB 00
       SPC 1
       END