at24cxx.c

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#include <Intrins.h>
#include <At89x51.h>
#include "constant.h"
#include "function.h"
#include "variable.h"
#include "chinese_const.h"

// first byte: 1010A2P1P2R/W
//#define EEPROM_ADDRESS 0XA0  	//device addresse:10100000
//#define AT24C08_A2_OPTION0 0X00	//A2 address :00000000 or 00001000
//#define AT24C08_A2_OPTION1 0X08
//#define AT24C08_PAGE0 0X00	//page address P1,P0:00000000
//#define AT24C08_PAGE1 0X02	//00000010
//#define AT24C08_PAGE2 0X04	//00000100
//#define AT24C08_PAGE3 0X06  //00000110
//#define I2C_EEPROM_READ		0X01
//#define I2C_EEPROM_WRITE 	0X00    //Read and Write:W-00000000,R-00000001

void I2c_Start()	//SDA,SCL=1 after start.
{
SDA=1;
SCL=1;
SDA=0;
I2c_Bus_Delay();
SCL=0;
I2c_Bus_Delay();
}	

//================================
/*send one byte(include address,device ID,data)*/
//================================
bit	I2c_Write_Byte(unsigned char byte)
{
unsigned char i=8, temp;
while(i--)
   {
	temp=byte;
	SDA=(bit)(temp&0x80);		//get bit7 of data
	byte<<=1;
	SCL=1;
	I2c_Bus_Delay();
	SCL=0;
   }
	SDA=1;			   //release bus for acknowledge
	I2c_Bus_Delay();
	SCL=1;
	I2c_Bus_Delay();
	SCL=0;
return SDA;		//return acknowledg signal
}

//=============================
unsigned char I2c_Read_Byte()
{
unsigned char Data=0,i=8;
SDA=1;
while(i--)
	{
		Data<<=1;
		SCL=1;
		I2c_Bus_Delay();
		Data|=SDA;
		SCL=0;
	}
return Data;
}
//============================
//send acknowledge signal
//1: no ack
//0: ack
//============================
void I2c_Send_Ack(bit Ack)
{
SDA=Ack;
SCL=1;
I2c_Bus_Delay();
SCL=0;
}
//=============================
//stop sent or read
//=============================
void I2c_Stop()
{
SCL=0;
SDA=0;
SCL=1;
I2c_Bus_Delay();
SDA=1;
I2c_Bus_Delay();		//don't need
}

//=============================================
//===7 uS delay time{3(nop)+2(ret)+2(acall)}===
//=============================================
void I2c_Bus_Delay()		
{
	_nop_();_nop_();
}
//=============================
// byte write,ack no check
//page:0--3 
//address:0-255
//=============================
void At24c08_Write_Byte(unsigned char page,unsigned char address,unsigned char byte)
{
	page<<=1;
	I2c_Start();
	I2c_Write_Byte(EEPROM_ADDRESS|page|AT24C08_A2_OPTION0|I2C_EEPROM_WRITE);
	I2c_Write_Byte(address);
	I2c_Write_Byte(byte);
  I2c_Stop();
}
//===============================
// byte random read,ack no check
//page:0--3 
//address:0-255
//===============================
unsigned char At24c08_Randomread_Byte(unsigned char page,unsigned char address)		
{
unsigned char i;
	page<<=1;
	I2c_Start();
	I2c_Write_Byte(EEPROM_ADDRESS|page|AT24C08_A2_OPTION0|I2C_EEPROM_WRITE);
	I2c_Write_Byte(address);
	I2c_Bus_Delay();  //restart
	I2c_Start();
	I2c_Write_Byte(EEPROM_ADDRESS|page|AT24C08_A2_OPTION0|I2C_EEPROM_READ);
	i=I2c_Read_Byte();
	I2c_Send_Ack(1);
	I2c_Stop();
	return i;
}