;======================================================================
;
; Author        : ADI - Apps              www.analog.com/MicroConverter
;
; Date          : 30 April 1999
;
; File          : master.asm
;
; Hardware      : ADuC812
;
; Description   : Code for a master in an I2C system.
;
; Reference     : Tech Note, uC001: "Using the ADuC812 I2C Interface"
;                 find it at www.analog.com/microconverter
;
;======================================================================

$MOD812                         ; use ADuC812 & 8052 predefined symbols

BITCNT          DATA    8h      ; bit counter for I2C routines
BYTECNT         DATA    030h    ; byte counter for I2C routines
SLAVEADD        DATA    032h    ; slave address for I2C routines

FLAGS           DATA    28h
NOACK           BIT     FLAGS.0 ; I2C no acknowledge flag
BUSY            BIT     FLAGS.1 ; I2C busy flag
ERROR           BIT     FLAGS.2 ; I2C error flag
MISTAKE         BIT     P3.4

;======================================================================

CSEG

ORG 0000H

        JMP START

;======================================================================

ORG 007BH                       ; Subroutines

;----------------------------------------------------------------------
; DELAY: Create a delay for the main signals ( SCLOCK , SDATA )
;----------------------------------------------------------------------

DELAY:

        NOP
        RET

;----------------------------------------------------------------------
; SENDSTOP: Send the bit stop of the transmission
;----------------------------------------------------------------------

SENDSTOP:

        SETB    MDE             ; to enable SDATA pin as an output
        CLR     MDO             ; get SDATA ready for stop
        SETB    MCO             ; set clock for stop
        ACALL   DELAY
        SETB    MDO             ; this is the stop bit
        CLR     BUSY            ; bus should be released
        RET

;----------------------------------------------------------------------
; SENDBYTE: Send a 8-bits word to the slave
;----------------------------------------------------------------------

SENDBYTE:

        MOV     BITCNT,#8       ; 8 bits in a byte

        SETB    MDE             ; to enable SDATA pin as an output	
        CLR     MDO
        CLR     MCO
LOOP:   RLC     A               ; send one bit
        MOV     MDO,C           ; put data bit on pin
        SETB    MCO             ; send clock
        CLR     MCO             ; clock is off
        DJNZ    BITCNT,LOOP

        CLR     MDE             ; release data line for acknowledge
        SETB    MCO             ; send clock for acknowledge
        JNB     MDI,NEXT        ; this is a check
        SETB    NOACK           ; no acknowledge		
NEXT:   CLR     MCO             ; clock for acknowledge
        RET


;----------------------------------------------------------------------
; BITSTART: Send the bit start of the transmission and the slave
;           address to the slave
;----------------------------------------------------------------------

BITSTART:

        SETB    BUSY            ; I2C is in progress
        SETB    MDE             ; to enable SDATA pin as an output
        CLR     NOACK
        CLR     ERROR
        JNB     MCO,FAULT
        JNB     MDO,FAULT
        CLR     MDO             ; this is
        ACALL   DELAY           ; the
        CLR     MCO             ; start bit
FAULT:  CLR     MISTAKE         ; set error flag
        MOV     A,SLAVEADD      ; Get slave address
        ACALL   SENDBYTE        ; call routine to send slave addr. byte
        RET

;----------------------------------------------------------------------
; SENDATA: Send all the sequence to the slave ( slave address + data )
;----------------------------------------------------------------------

SENDATA:

        ACALL   BITSTART
        JB      MDI,NEXT1
        MOV     A,#00
SLOOP:  MOVX    A,@DPTR
        ACALL   SENDBYTE
        INC     DPTR
        JB      NOACK,NEXT1
        DJNZ    BYTECNT,SLOOP

NEXT1:  ACALL   SENDSTOP
        MOV     A,FLAGS
        ANL     A,#07h
        JZ      RETOUR
        SETB    P3.4
        CLR     I2CRS
RETOUR: RET

;----------------------------------------------------------------------
; RCVBYTE: receives one byte of data from an I2C slave device.
;----------------------------------------------------------------------

RCVBYTE:

        MOV     BITCNT,#8       ;Set bit count.

        CLR     MDE             ;Data pin of the master is now an input
        CLR     MCO
LOOP2:  SETB    MCO
        CLR     MCO
        MOV     C,MDI           ;Get data bit from pin.
        RLC     A               ;Rotate bit into result byte.

        DJNZ    BITCNT,LOOP2    ;Repeat until all bits received.

                                ;result byte is in the accumulator

        PUSH    ACC             ;Save result byte in the stack

        SETB    MDE             ;Data pin of the master must be an..
                                ;..output for the acknowledge	
        MOV     A,BYTECNT
        CJNE    A,#1,SACK       ;Check for last byte of frame.
        SETB    MDO             ;Send no acknowledge on last byte.
        SJMP    NACK

SACK:   CLR     MDO             ;Send acknowledge bit.

NACK:   SETB    MCO             ;Send acknowledge clock.
        POP     ACC             ;Restore accumulator
        ACALL   DELAY
        CLR     MCO
        SETB    MDO             ;Clear acknowledge bit.
        ACALL   DELAY
        CLR     MDE

        RET

;----------------------------------------------------------------------
; RCVDATA: receives one or more bytes of data from an I2C slave device.
;----------------------------------------------------------------------

RCVDATA:   INC     SLAVEADD       ;Set for READ of slave.
           ACALL   BITSTART       ;Acquire bus and send slave address.
           JB      NoAck,RDEX     ;Check for slave not responding.

RDLoop:    ACALL   RCVBYTE        ;Receive next data byte.
           MOV     @R1,A          ;Save data byte in buffer.
           INC     R1             ;Advance buffer pointer.
           DJNZ    BYTECNT,RDLoop ;Repeat untill all bytes received.

RDEX:      ACALL   SENDSTOP       ;Done, send an I2C stop.
           RET

;======================================================================
; Main program
;======================================================================

START:

        MOV     SP,#040h		
        CLR     NOACK
        MOV     SLAVEADD,#088H
        MOV     BYTECNT,#3
        MOV     I2CCON,#0A8h

; code for a write mode ( master-transmitter to slave-receiver )

;       MOV    	DPTR,#080H      ; master transmits to slave
;       MOV    	A,#055H         ; datas which are located in
;       MOVX   	@DPTR,A         ; the external memory
;       MOV    	DPTR,#081H
;       MOV    	A,#044H
;       MOVX   	@DPTR,A
;       MOV    	DPTR,#082H
;       MOV    	A,#033H
;       MOVX   	@DPTR,A

;       MOV     DPTR,#080h
;       ACALL   SENDATA

; code for a read mode ( master reads immediately after first byte )

        MOV     R1,#035h
        ACALL   RCVDATA

END