;********************************************************************
;                 All rate calculations assume an 11.0592MHz Mclk.
;	This program run display port 3 value on LCD : 
;	
;	Author : Guy Bami Sens. Syst Master
;********************************************************************
$MOD812                         ; Use 8052&ADuC812 predefined symbols
$NOPRINT		; do not generate .lst file

LED     	EQU     P3.4            	; P3.4 drives red LED on eval board

SCL 	EQU     P2.1	;clock
SDA 	EQU     P2.2	;data of I2C
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            ; jump to main program
;________________________________________________________________
                                             ; INTERRUPT VECTOR SPACE
;==============================================================
ORG 007BH                       ; Subroutines

;----------------------------------------------------------------------
; BITSTART: Send the bit start of the transmission and the slave
;           address to the slave
;----------------------------------------------------------------------
BITSTART:
	setb 	LED	;switch LED
        	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 the start bit
	CLR     SDA
        	LCALL   DELAY    
        	CLR     MCO            
	CLR	SCL
        FAULT:  
	CLR     MISTAKE         	; set error flag
        	MOV     A, SLAVEADD      	; Get slave address
        	LCALL   SENDBYTE        	; call routine to send slave addr. byte
	CLR     MISTAKE         	; set error flag
        RET
;----------------------------------------------------------------------
; SENDSTOP: Send the bit stop of the transmission
;----------------------------------------------------------------------

SENDSTOP:
	clr 	LED	;switch LED
        	SETB    MDE             ; to enable SDATA pin as an output
        	CLR     MDO             ; get SDATA ready for stop
	CLR	SDA
        	SETB    MCO             ; set clock for stop
	SETB    SCL
        	LCALL   DELAY
       	SETB    MDO             ; this is the stop bit
	SETB   SDA
	
        	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
	clr     SDA	
	clr    SCL
       LOOP:   
	RLC     A               		; send one bit
        	MOV     MDO,C           	; put data bit on pin
	mov   SDA,C
        	SETB    MCO             	; send clock
        	CLR     MCO             		; clock is off
	setb	SDA
	clr	SCL	

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

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

DELAY:
        	NOP
        	RET



START:
	MOV     SP,#040h		
        	CLR     NOACK
        	MOV     SLAVEADD,#074H
        	MOV     BYTECNT,#3
        	MOV     I2CCON,#0A8h
	MOV     SLAVEADD,#074H

	LCALL 	BITSTART
	MOV	A, #074h	;send address slave for write
	LCALL 	SENDBYTE

	MOV	A, #00h	;send the control byte for fonction set RS = 0
	LCALL 	SENDBYTE

	MOV	A, #2Ch	;send  fonction set for 4-lines display
	LCALL 	SENDBYTE

	MOV	A, #0Eh	;turns ON display and cursor
	LCALL 	SENDBYTE

	MOV	A, #00h	;send the entry mode set(increment cursor by 1 and shift right)
	LCALL 	SENDBYTE

	MOV	A, #40h	;send the control byte for fonction set RS = 1
	LCALL 	SENDBYTE

	MOV	A, #74h	;send address slave for write
	LCALL 	SENDBYTE

	MOV	A, #40h	;send the control byte for write data
	LCALL 	SENDBYTE


	MOV	A, #50h	;write to DDRAM (value ' P_ ' )
	LCALL 	SENDBYTE

	MOV	A, #48h	;write to DDRAM (value ' PH_ ' )
	LCALL 	SENDBYTE

	MOV	A, #80h	;send a control byte (value ' PH_ ' )
	LCALL 	SENDBYTE

	LCALL	SENDSTOP
	JMP	START



	
END