数据有效性：
起始和终止信号时序：
设备地址：
写字节时序：
读数据时序：
函数模拟 IIC 总线 时序：
/**************************************//******模拟I2C总线操作函数*************//**************************************///延时函数void Delay(){ ; ; }//初始化void I2C_Init(){ SDA = 1; SCL = 1;}//起始信号void I2C_Start(){ SDA = 1; Delay(); SCL = 1; Delay(); SDA = 0; Delay();}//终止信号void I2C_Stop(){ SDA = 0; Delay(); SCL = 1; Delay(); SDA = 1; Delay();}//应答信号void I2C_Acknowledge(){ unsigned char i; SCL = 1; Delay(); while((SDA == 1) && (i<250)){ //在一定时间内等待应答信号 i++; } SCL = 0; Delay();}//写一个字节void I2C_WriteByte(unsigned char Data){ unsigned char i,temp; temp = Data; SCL = 0; Delay(); for(i = 0;i < 8;i++){ temp = temp<<1; SDA = CY; //CY为PSW寄存器的溢出位 Delay(); SCL = 1; Delay(); SCL = 0; Delay(); } SDA = 1; Delay();}//读一个字节unsigned char I2C_ReadByte(){ unsigned char i,temp,Data; SCL = 0; Delay(); SDA = 1; Delay(); for(i = 0;i < 8;i++){ SCL = 1; Delay(); temp = SDA; Data = (Data<<1)|temp; SCL = 0; Delay(); } return Data;}//在特定位置写一个字节数据void I2C_WriteByteAt(unsigned char address,unsigned char Data){ I2C_Init(); I2C_Start(); I2C_WriteByte(0xa0);//写器件地址，最后一位表示数据方向 I2C_Acknowledge(); I2C_WriteByte(address);//写存储地址 I2C_Acknowledge(); I2C_WriteByte(Data);//写数据 I2C_Acknowledge(); I2C_Stop();}//从特定位置读一个字节数据unsigned char I2C_ReadByteAt(unsigned char address){ unsigned char Data; I2C_Init(); I2C_Start(); I2C_WriteByte(0xa0);//写器件地址，最后一位表示数据方向 I2C_Acknowledge(); I2C_WriteByte(address);//写存储地址 I2C_Acknowledge(); I2C_Start(); I2C_WriteByte(0xa1);//再次写器件地址，注意改变数据方向 I2C_Acknowledge(); Data = I2C_ReadByte();//读数据 I2C_Stop(); return Data;}