C51:24C02 write and read one byte

#include //Header file containing _nop_() function definition
#define OP_READ 0xa1 //Device address and read operation, 0xa1 is 1010 0001B
#define OP_WRITE 0xa0 //Device address and write operation, 0xa1 is 1010 0000B
sbit SDA=P3^4; //Define the serial data bus SDA bit as the P3.4 pin
sbit SCL=P3^3; //Define the serial clock bus SDA bit as the P3.3 pin

//Function: Delay 1ms (3j+2)*i=(3×33+2)×10=1010 (microseconds), which can be considered as 1 millisecond
void delay1ms()
{
   unsigned char i,j; 
  for(i=0;i<10;i++)
   for(j=0;j<33;j++)
    ;   
 }

//Function: delay for several milliseconds
 void delaynms(unsigned char n)
 {
   unsigned char i;
 for(i=0;i     delay1ms();
 }

//Function: start data transmission

void start()
{
 SDA = 1; //SDA is initialized to high level "1"
   SCL = 1; //When starting data transmission, SCL is required to be high level "1"
 _nop_(); //Wait for one machine cycle
 _nop_(
 ); //Wait for one machine cycle
 _nop_(); //Wait for one machine cycle
 SDA = 0; //The falling edge of SDA is considered to be the start signal
 _nop_(); //Wait for one machine cycle
 _nop_
 (); //Wait for one machine cycle _nop_
 (); //Wait for one machine cycle
 SCL = 0; //When SCL is low, the data on SDA is allowed to change (that is, subsequent data transmission is allowed)  
}
//Function: End data transmission 
void stop()
// Stop bit
{
 SDA = 0; //SDA is initialized to low level "0" _n
 SCL = 1; //When ending data transmission, SCL is required to be high level "1"
 _nop_(); //Wait for a machine cycle_nop_
 (); //Wait for a machine cycle_nop_
 (); //Wait for a machine cycle_nop_
 (); //Wait for a machine cycleSDA
 = 1; //The rising edge of SDA is considered the end signal_nop_
 (); //Wait for a machine cycle_nop_
 (); //Wait for a machine cycle_nop_
 (); //Wait for a machine cycle_nop_
 (); //Wait for a machine cycleSDA
 =0;
 SCL=0;
}

//Function: Read a byte from AT24Cxx
unsigned char ReadData()
// Move data from AT24Cxx to MCU
{
 unsigned char i;
 unsigned char x; //Store data read from AT24Cxx
 for(i = 0; i < 8; i++)
 {
  SCL = 1; //Set SCL to high level
  x<<=1; //Shift each binary bit in x one position to the left
  x|=(unsigned char)SDA; //Store the data on SDA into x through bitwise "OR" operation
  SCL = 0; //Read data on the falling edge of SCL
 }
 return(x); //Return the read data
}

//Answer check
bit ack()
{
 bit ack_bit;
 SDA = 1; // The sending device (host) should release the SDA line during the high level period of the clock pulse (SCL=1),
                 //so that the SDA line can be controlled by the receiving device (AT24Cxx)
 _nop_(); //Wait for a machine cycle 
 _nop_(); //Wait for a machine cycle 
 SCL = 1; //According to the above regulations, SCL should be high
 _nop_(); //Wait for a machine cycle _nop_(); //Wait for a 
 machine cycle _nop_ 
 (); //Wait for a machine cycle 
 _nop_(); //Wait for a machine cycle 
 ack_bit = SDA; //The receiving device (AT24Cxx) sends a low level to SDA, indicating that a byte has been received.
                //If a high level is sent, it means that it has not been received and the transmission is abnormal
 SCL = 0; //When SCL is low, the data on SDA is allowed to change (that is, subsequent data transmission is allowed)
 return ack_bit; 
}

//Write a byte
//Before calling this data write function, you need to call the start function start() first, so SCL=0
void WriteCurrent(unsigned char y)
{
 unsigned char i;
    for(i = 0; i < 8; i++) // Shift in 8 bits in a loop
 {
     SDA = (bit)(y&0x80); //Send the highest bit of data to S through the bitwise "AND" operation
                                    //Because the high bit is in front and the low bit is in the back during transmission
  _nop_(); //Wait for one machine cycle   
    SCL = 1; //Write data to AT24Cxx on the rising edge of SCL      
    _nop_(); //Wait for one machine cycle 
   _nop_(); //Wait for one machine cycle       
  
    SCL = 0; //Reset SCL to low level to form the 8 pulses required to transmit data on the SCL line
  y <<= 1; //Shift each binary bit in y one bit to the left
 }
    //Return AT24Cxx acknowledgement bit
}

/***************************************************
Function: Main function
************************************************/
main(void)
{
 //Data writing process:
 //Start-write chip addressing-response-write data first address-response-write data-response-termination signalstart
 (); //Start data transferWriteCurrent
 (0xa0); //Select the AT24Cxx chip to be operated, and inform it to write dataack
 ();
 WriteCurrent(0x36); //Write to the specified address 0x36
 ack();

 WriteCurrent(0x00); //Write data 0x00 to the current address (the address specified above)
 ack();
 stop(); //Stop data transfer
 delaynms(4); 

 //Read data flow:
 //Start-write chip addressing-response-write data first address-response-restart-write chip addressing-response-read datastart
 ();                      
 WriteCurrent(0xa0); //Select the AT24Cxx chip to be operated, and inform it to write dataack
 ();
 WriteCurrent(0x36); //Read data addressack
 ();

 start();              
 WriteCurrent(0xa1); //Select the AT24Cxx chip to be operated and tell it to read its data
 ack();
 P1=ReadData(); //Store the read data into P1
 stop(); //Stop data transmission

}