;======================================================================
;
; Author        : ADI - Apps              www.analog.com/MicroConverter
;
; Date          : 30 April 1999
;
; File          : slave.asm
;
; Hardware      : ADuC812
;
; Description   : Code for a slave 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

BYTECNT         DATA    030h    ; byte counter for I2C routines

FLAGS           DATA    28h
GO              BIT     FLAGS.0 ; flag for all the interrupts
RC              BIT     FLAGS.1 ; flag for Write mode interrupt
TR              BIT     FLAGS.2 ; flag for Read mode interrupt

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

CSEG

ORG 0000H

        JMP START

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

ORG 003Bh                       ; I2C slave interrupt

        JB      RC,RECEIVE      ; depending on flags there
        JB      TR,TRANSMIT     ; are two different interrupts

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

ORG 007BH                       ; Subroutines

;----------------------------------------------------------------------
; RECEIVE: receive interrupt routine
;----------------------------------------------------------------------

RECEIVE:
        SETB    GO
        MOV     @R1,I2CDAT      ; move data on internal RAM
        CLR     I2CI            ; clear interrupt bit
        RETI

;----------------------------------------------------------------------
; TRANSMIT: transmit interrupt routine
;----------------------------------------------------------------------

TRANSMIT:
        SETB    GO
        MOV     I2CDAT,R0
        CLR     I2CI            ; clear interrupt bit
        RETI

;----------------------------------------------------------------------
; RCVBYTE2: receive byte routine for read mode
;----------------------------------------------------------------------

RCVBYTE2:

        NOP
        RET

;----------------------------------------------------------------------
; RCVBYTE: receive byte routine
;----------------------------------------------------------------------

RCVBYTE:

        JNB     GO,$            ; wait for the interrupt
        INC     R1              ; next storage will be on 41h then 42h
        CLR     GO              ; flag cleared for the next interrupt
        RET

;----------------------------------------------------------------------
; RCVDATA: receive bytes routine
;----------------------------------------------------------------------

RCVDATA:

        MOV     BYTECNT,#4      ; 4 bytes : address + 3 datas
LOOP2:  ACALL   RCVBYTE
        DJNZ    BYTECNT,LOOP2
        RET

;----------------------------------------------------------------------
; SENDBYTE: byte transmit routine
;----------------------------------------------------------------------

SENDBYTE:

        JNB     GO,$            ; wait for the interrupt
        INC     R0              ; 2nd data is 34h and 3rd data is 35h
        CLR     GO
        RET

;----------------------------------------------------------------------
;SENDATA:bytes transmit routine
;----------------------------------------------------------------------

SENDATA:

        MOV     BYTECNT,#3      ; 3 data will be send by the slave
LOOP:   ACALL   SENDBYTE
        DJNZ    BYTECNT,LOOP
        RET

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

START:

        CLR     GO              ; clear flag used in the interrupt
        MOV     I2CADD,#044h    ; slave address
        MOV     SP,#020h
        MOV     IE,#80h         ; enable all the interrupts
        MOV     IE2,#01h        ; enable I2C interrupt
        MOV     I2CCON,#000h    ; slave mode

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

;       SETB    RC              ; specific flag for interrupt routine
;       MOV     R1,#040h        ; first data to be stored in RAM at 40h	
;       ACALL   RCVDATA         ; slave receives his address + 3 datas

; code for read mode ( master reads slave immediately after 1st byte )

        SETB    RC              ; specific flag for interrupt routine
        MOV     R0,#033h        ; first data send is 33h
        ACALL   RCVBYTE2        ; slave receives address send by master
        CLR     RC
        SETB    TR
        ACALL   SENDATA         ; slave sends 3 datas

        SETB     P3.4            ; led is off, everything is OK

END