; Nixie-Uhr-Programm mit Bitbanging für I2C

; Register-Definitionen
HOUR   EQU R0
MINUTE EQU R1
SECOND EQU R2
MODE   EQU R3

; Tasten-Definitionen
HOUR_INC EQU P1.2
HOUR_DEC EQU P1.3
MIN_INC  EQU P1.4
MIN_DEC  EQU P1.5

; 8255-Definitionen
PORTA EQU 0FFH ; Stunden
PORTB EQU 0FEH ; Minuten

; 74141-Definitionen
IC1 EQU PORTA ; Stunden
IC2 EQU PORTB ; Minuten

; PCF8563-Definitionen
PCF8563_ADDR EQU 0A2H ; I2C-Adresse
PCF8563_SEC  EQU 2 ; Sekunden-Register
PCF8563_MIN  EQU 3 ; Minuten-Register
PCF8563_HOUR EQU 4 ; Stunden-Register

; I2C-Pins
SCL EQU P1.0
SDA EQU P1.1

; Bitbanging-Funktionen für I2C
I2C_START:
  SETB SDA
  SETB SCL
  CLR SDA
  CLR SCL
  RET

I2C_STOP:
  CLR SDA
  SETB SCL
  SETB SDA
  RET

I2C_WRITE_BYTE:
  MOV R4, #8
I2C_WRITE_LOOP:
  RLC A
  MOV SDA, C
  SETB SCL
  CLR SCL
  DJNZ R4, I2C_WRITE_LOOP
  RET

I2C_READ_BYTE:
  MOV R4, #8
I2C_READ_LOOP:
  SETB SCL
  MOV C, SDA
  RLC A
  CLR SCL
  DJNZ R4, I2C_READ_LOOP
  RET

; Programm-Start
ORG 0
MOV HOUR, #12 ; Start-Stunde
MOV MINUTE, #0 ; Start-Minute
MOV SECOND, #0 ; Start-Sekunde
MOV MODE, #0 ; Start-Modus

; Hauptschleife
LOOP:
  ; Tasten abfragen
  JB HOUR_INC, HOUR_INC_PRESSED
  JB HOUR_DEC, HOUR_DEC_PRESSED
  JB MIN_INC, MIN_INC_PRESSED
  JB MIN_DEC, MIN_DEC_PRESSED

  ; Zeit von PCF8563 lesen
  CALL I2C_START
  MOV A, #PCF8563_ADDR
  CALL I2C_WRITE_BYTE
  MOV A, #PCF8563_SEC
  CALL I2C_WRITE_BYTE
  CALL I2C_START
  MOV A, #PCF8563_ADDR + 1
  CALL I2C_WRITE_BYTE
  CALL I2C_READ_BYTE
  MOV SECOND, A
  CALL I2C_READ_BYTE
  MOV MINUTE, A
  CALL I2C_READ_BYTE
  MOV HOUR, A
  CALL I2C_STOP

  ; Anzeige aktualisieren
  MOV A, HOUR
  ANL A, #0FH
  MOV IC1, A
  MOV A, HOUR
  SWAP A
  ANL A, #0FH
  MOV IC1, A
  MOV A, MINUTE
  ANL A, #0FH
  MOV IC2, A
  MOV A, MINUTE
  SWAP A
  ANL A, #0FH
  MOV IC2, A

  ; Zurück zur Hauptschleife
  JMP LOOP

; Tasten-Handler
HOUR_INC_PRESSED:
  INC HOUR
  CJNE HOUR, #24, HOUR_INC_DONE
  MOV HOUR, #0
  CALL I2C_START
  MOV A, #PCF8563_ADDR
  CALL I2C_WRITE_BYTE
  MOV A, #PCF8563_HOUR
  CALL I2C_WRITE_BYTE
  MOV A, HOUR
  CALL I2C_WRITE_BYTE
  CALL I2C_STOP
HOUR_INC_DONE:
  JMP LOOP

HOUR_DEC_PRESSED:
  DEC HOUR
  CJNE HOUR, #255, HOUR_DEC_DONE
  MOV HOUR, #23
  CALL I2C_START
  MOV A, #PCF8563_ADDR
  CALL I2C_WRITE_BYTE
  MOV A, #PCF8563_HOUR
  CALL I2C_WRITE_BYTE
  MOV A, HOUR
  CALL I2C_WRITE_BYTE
  CALL I2C_STOP
HOUR_DEC_DONE:
  JMP LOOP

MIN_INC_PRESSED:
  INC MINUTE
  CJNE MINUTE, #60, MIN_INC_DONE
  MOV MINUTE, #0
  CALL I2C_START
  MOV A, #PCF8563_ADDR
  CALL I2C_WRITE_BYTE
  MOV A, #PCF8563_MIN
  CALL I2C_WRITE_BYTE
  MOV A, MINUTE
  CALL I2C_WRITE_BYTE
  CALL I2C_STOP
MIN_INC_DONE:
  JMP LOOP

MIN_DEC_PRESSED:
  DEC MINUTE
  CJNE MINUTE, #255, MIN_DEC_DONE
  MOV MINUTE, #59
  CALL I2C_START
  MOV A, #PCF8563_ADDR
  CALL I2C_WRITE_BYTE
  MOV A, #PCF8563_MIN
  CALL I2C_WRITE_BYTE
  MOV A, MINUTE
  CALL I2C_WRITE_BYTE
  CALL I2C_STOP
MIN_DEC_DONE:
  JMP LOOP

END