Interrupt serial communication

First example:

Avoid infinite loop, keep sending data (use the self-set receiving data flag method, do not turn off the serial port interrupt ES method) The flag must be placed at the last position in the if statement, otherwise an infinite loop will occur

#include
#define uchar unsigned char
#define uint unsigned int
uchar flag=0,temp;
void init()
{
 TMOD=0X20; //Timer 1 mode 2 as baud rate generator
 TH1=0XF3; //Install the initial baud rate to 4800bps
 TL1=0XF3;
 TR1=1; //Start timer 1
 SCON=0X50; //Set the serial port working mode to mode 1
 PCON=0X80; // Double the baud rate to 4800
 EA=1; //Open the general interrupt
 ES=1; //Enable serial port interrupt
 TI=0; // Clear the send interrupt flag
 RI=0; // Clear the receive interrupt flag
}
void main()
{
 init();
 while(1)
 {
  if(flag==1)
  {
   //ES=0; //flag is 1, indicating that the reception caused an interrupt
   //flag=0; //clear interrupt flag
   RI=0; // Clear the receive interrupt flag to prepare for the next frame of data reception
   temp=SBUF; //Read in received data. Without disabling interrupt ES, the CPU will not cause an interrupt when reading received data.

The receiving data is automatically executed by the receiving SBUF receiving buffer
   P0=temp; //Read data and send to P0 port
   SBUF=temp; //Return received data to the sender
   //TI=0; //Wait for the data to be sent, otherwise TI=0, flag=0 has been executed before the data is sent.
   //flag=0; //After sending, it causes an interrupt, and the flag is set to 1 again, entering an infinite loop and continuously sending data
   while(!TI);//Wait for sending to complete! ! Keep waiting! !
      TI=0; //After data transmission, clear the transmission interrupt flag to prepare for the next frame of data transmission
   flag=0; //Must have otherwise enter an infinite loop, put last
   //ES=1; //Allow serial port interrupt to continue receiving data
  }
 }
}
void serial() interrupt 4
{
 flag=1;
}

----------------------Example 2:-------------------------------------------------------

/**********************************************
      Interrupt serial communication (using the ES method to disable serial interrupts) is recommended to avoid frame loss
*************************************************/
#include
#define uchar unsigned char
#define uint unsigned int
uchar flag=0,temp;
void init()
{
 TMOD=0X20; //Timer 1 mode 2 as baud rate generator
 TH1=0XF3; //Install the initial baud rate to 4800bps
 TL1=0XF3;
 TR1=1; //Start timer 1
 SCON=0X50; //Set the serial port working mode to mode 1
 PCON=0X80; // Double the baud rate to 4800
 EA=1; //Open the general interrupt
 ES=1; //Enable serial port interrupt
 TI=0; // Clear the send interrupt flag
 RI=0; // Clear the receive interrupt flag
}
void main()
{
 init();
 while(1)
 {
  if(flag==1)
  {
   ES=0; //flag is 1, indicating that the reception has completed and caused an interrupt, turn off the serial port interrupt, and process the current frame
   flag=0; // clear interrupt flag
   RI=0; // Clear the receive interrupt flag to prepare for receiving the next frame of data. Clearing it here will not cause frame loss.
   temp=SBUF; //Read in received data. If the interrupt ES is not disabled, the CPU will not cause an interrupt when reading received data.

The receiving data is automatically executed by the receiving SBUF receiving buffer
   P0=temp; //Read data and send to P0 port
   SBUF=temp; //Return received data to the sender
   //TI=0; //Wait for the data to be sent, otherwise TI=0, flag=0 has been executed before the data is sent.
   //flag=0; //After sending, it causes an interrupt, and the flag is set to 1 again, entering an infinite loop and continuously sending data
   while(!TI);//Wait for sending to complete! ! Keep waiting! !
      TI=0; //After data transmission, clear the transmission interrupt flag to prepare for the next frame of data transmission
   //flag=0; //Must have otherwise enter an infinite loop, put last
   ES=1; // Allow serial port interrupt to continue receiving data
  }
 }
}
void serial() interrupt 4 //Execute this sentence to generate an interrupt indicating that the data has been received
{
    //RI=0; //Do not clear the receive interrupt flag here, otherwise the receiving SUBF will be in the receiving state.

The interruption continues to affect other instructions, causing the return frame loss phenomenon. The experiment shows that
 flag=1;
}