$INCLUDE   (reg_c51.INC)

TWI_data DATA 10H;
slave_adr DATA 11H;
rw BIT 20H;                         /* 0=write, 1=read */
b_TWI_busy BIT 21H;

org 000h
ljmp begin
org 43h
ljmp twi_it

;/**
; * FUNCTION_PURPOSE:this function setup TWI in master mode and sends data to slave.
; * FUNCTION_INPUTS:void
; * FUNCTION_OUTPUTS:void
; */
org 0100h

begin:
 clr p0.4

ORL SSCON,#40h;                     /* enable TWI */
SETB EA;                            /* interrupt enable */
ORL IEN1,#02h;                      /* enable TWI interrupt */


;---- Ansprechen Sensor und Reg. 0 -------------------
CLR b_TWI_busy
loop:                               /* end less */

JB b_TWI_busy,end_if
MOV ACC,SSCON
JB ACC.4,end_if
   SETB b_TWI_busy;                    /* flag busy =1 */
   MOV TWI_data,#00h;                  /* data example to send */
   MOV slave_adr,#0x70;                 /* slave adresse example */
   CLR rw;                             /* 0=write */
   MOV SSDAT,#00h;                     /* clear buffer before sending data */
   ORL SSCON,#20h;                     /* TWI start sending */
CLR p0.0 
end_if:

JMP loop

;---- Ansprechen Sensor und Befehl Messen -------------------
CLR b_TWI_busy
loop1:                               /* end less */

JB b_TWI_busy,end_if1
MOV ACC,SSCON
JB ACC.4,end_if
   SETB b_TWI_busy;                    /* flag busy =1 */
   MOV TWI_data,#51h;                  /* data example to send */
   MOV slave_adr,#0x70;                 /* slave adresse example */
   CLR rw;                             /* 0=write */
   MOV SSDAT,#00h;                     /* clear buffer before sending data */
   ORL SSCON,#20h;                     /* TWI start sending */
clr p0.1
end_if1:

JMP loop1

Ljmp warten

;---- Ansprechen Sensor und Register "niedriger Wert" auslesen -------------------
CLR b_TWI_busy
loop2:                               /* end less */

JB b_TWI_busy,end_if2
MOV ACC,SSCON
JB ACC.4,end_if
   SETB b_TWI_busy;                    /* flag busy =1 */
   MOV TWI_data,#02h;                  /* data example to send */
   MOV slave_adr,#0x70;                 /* slave adresse example */
   setb rw;                             /* 0=write */
   MOV SSDAT,#00h;                     /* clear buffer before sending data */
   ORL SSCON,#20h;                     /* TWI start sending */
clr p0.2
end_if2:

JMP loop2


;---- Ansprechen Sensor und Register "hoher Wert" auslesen -------------------
CLR b_TWI_busy
loop3:                               /* end less */

JB b_TWI_busy,end_if3
MOV ACC,SSCON
JB ACC.4,end_if
   SETB b_TWI_busy;                    /* flag busy =1 */
   MOV TWI_data,#03h;                  /* data example to send */
   MOV slave_adr,#0x70;                 /* slave adresse example */
   setb rw;                             /* 0=write */
   MOV SSDAT,#00h;                     /* clear buffer before sending data */
   ORL SSCON,#20h;                     /* TWI start sending */
clr p0.3
end_if3:

JMP loop3

 





;--------------Intrerruptroutinen----------------------------------------------
									;/**
									; * FUNCTION_PURPOSE:TWI interrupt, task witch process the different status of TWI
									; * FUNCTION_INPUTS:void
									; * FUNCTION_OUTPUTS:void
									; */
twi_it:
MOV R7,SSCS

								;	/* TWI status tasking */
   
      CJNE R7,#00h,end_case_00;     /* A start condition has been sent */
                                    /* SLR+R/W are transmitted, ACK bit received */
      CLR b_TWI_busy;               /* TWI is free */
      JMP end_switch
      end_case_00:
      

      CJNE R7,#08h,end_case_08;     /* A start condition has been sent */
                                    /* SLR+R/W are transmitted, ACK bit received */
      ANL SSCON,#~20h;             	/* clear start condition */
    								/* send slave adress and read/write bit */
      MOV ACC,slave_adr
      RL A
      MOV C,rw
      MOV ACC.0,C
      MOV SSDAT,A

      ORL SSCON,#04h;               /* set AA */
      JMP end_switch
      end_case_08:


      CJNE R7,#10h,end_case_10;     /* A repeated start condition has been sent */
                                 	/* SLR+R/W are transmitted, ACK bit received */
      ANL SSCON,#~20h;         	    /* clear start condition */
     								/* send slave adress and read/write bit */
      MOV ACC,slave_adr
      RL  A
      MOV C,rw
      MOV ACC.0,C
      MOV SSDAT,A

      ORL SSCON,#04h;               /* set AA */
      JMP end_switch
      end_case_10:


      CJNE R7,#18h,end_case_18;     /* SLR+W was transmitted, ACK bit received */
      MOV SSDAT,TWI_data;           /* Transmit data byte, ACK bit received */
      ORL SSCON,#04h;               /* set AA */
      JMP end_switch
      end_case_18:

      CJNE R7,#20h,end_case_20;     /* SLR+W was transmitted, NOT ACK bit received */
      ORL SSCON,#10h;               /* Transmit STOP */
      CLR b_TWI_busy;               /* TWI is free */
      JMP end_switch
      end_case_20:

      CJNE R7,#28h,end_case_28;     /* DATA was transmitted, ACK bit received */
      ORL SSCON,#10h;               /* send STOP */
      CLR b_TWI_busy;               /* TWI is free */
      JMP end_switch
      end_case_28:

      CJNE R7,#30h,end_case_30;     /* DATA was transmitted, NOT ACK bit received */
      ORL SSCON,#10h;               /* Transmit STOP */
      CLR b_TWI_busy;               /* TWI is free */
      JMP end_switch
      end_case_30:

      CJNE R7,#38h,end_case_38;     /* Arbitration lost in SLA+W or DATA.  */
      ORL SSCON,#10h;               /* Transmit STOP */
      CLR b_TWI_busy;               /* TWI is free */
      JMP end_switch
      end_case_38:
   
end_switch:
ANL SSCON,#~08;                     /* clear flag */
RETI




warten:	mov   R7, #09h
      	mov   R6, #00h
      	mov   R5, #00h
      	inc   R7
      	inc   R6
       	inc   R5
warte: 	djnz  R5, $
       	djnz  R6, warte
       	djnz  R7, warte
       	ret









end