//Name:  I2C standard program
//Author: Ares
//Date:    2005.11.4

＃i nclude <AT89X52.H>
＃i nclude <intrins.h>

sbit SDA=P2^5;
sbit SCL=P1^0;

#define uchar unsigned char
#define uint unsigned int
#define byte unsigned char

void delay()
{
_nop_();
_nop_();
_nop_();
_nop_();
_nop_();
}

void delayms (uint x)
{
 byte j;
 while(x--){
    for(j=0;j<125;j++){;}
      }
}

void I2C_Start()                      //I2C START
{
 SDA=1;
 _nop_();
  SCL=1;
  delay();
   SDA=0;
   delay();
  SCL=0;
  _nop_();
}

void I2C_Stop()             //I2C STOP
{
SDA=0;
_nop_();
SCL=1;
delay();
SDA=1;
delay();
}

bit  I2C_ReceiveAck()
{
bit ck;
SDA=1;                  //THE HOST RELEASE THE BUS
_nop_();
_nop_();
SCL=1;          
_nop_();
_nop_();
ck=SDA;
_nop_();
_nop_();
SCL=0;
_nop_();
return(ck);
}

void I2C_SendAck()

{
SDA=0;
_nop_();
_nop_();
SCL=1;
delay();          //remain
SCL=0;
_nop_();
_nop_();
}

void I2C_SendNoAck()

{
SDA=1;
_nop_();
_nop_();
SCL=1;
delay();   //remain
SCL=0;
_nop_();
_nop_();
}

void I2C_SendByte(byte SData)
{uchar i;
for(i=0;i<8;i++)
{  SDA=(bit)(SData&0x80);
   SData=SData<<1;
   SCL=1;
   delay();
   SCL=0;
}
}

byte I2C_ReceiveByte()
{uchar i;
 byte RData;
 RData=0;

for(i=0;i<8;i++)
{  SDA=1;
  _nop_();
  SCL=1;
  _nop_();
  _nop_();
  RData=RData<<1;
  RData=RData|SDA;
  _nop_();
  _nop_();
  SCL=0;
}
return(RData);
}

void I2C_SendToSubAddress(byte SlaveAddress,byte SubAddress,byte *pSData,uchar N)
{uchar i;
I2C_Start();
I2C_SendByte(SlaveAddress);    //send slave address(write device)
I2C_ReceiveAck();
I2C_SendByte(SubAddress);    //send sub address
I2C_ReceiveAck();

for(i=0;i<N;i++)
{
  I2C_SendByte(pSData[i]);
  I2C_ReceiveAck();
}
I2C_Stop();
}

void I2C_ReceiveFromSubAddress(byte SlaveAddress,byte SubAddress,byte *pRData,uchar N)
{uchar i;
I2C_Start();
I2C_SendByte(SlaveAddress);    //send slave address(write device)
I2C_ReceiveAck();
I2C_SendByte(SubAddress);    //send sub address
I2C_ReceiveAck();
I2C_Start();                              //I2C Start Again!
I2C_SendByte(SlaveAddress+1);    //send slave address(read device)
I2C_ReceiveAck();
for(i=0;i<N-1;i++)
{
   pRData[i]=I2C_ReceiveByte();
   I2C_SendAck();
}
pRData[i]=I2C_ReceiveByte();
I2C_SendNoAck();
I2C_Stop();
}

main()
{byte *pData;
  byte a[16]={0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
  pData=a;
I2C_ReceiveFromSubAddress(0xA0,0x20,pData,16);
I2C_SendToSubAddress(0xA0,0,pData,16);
}