DSP 28335 TTL SCI serial port communication error cannot enter and receive

The project communicates between the two DSP28335 through the ordinary SCI serial port, one master and one slave. The host sends instructions to the slave, triggers the slave SCI reception interrupt, performs packet judgment and storage during the interrupt, and data processing and reply are carried out in the main loop, and FIFO is not used, and is sent in a polling manner.

1: The master and slave are turned on at the same time, the master and slave communication are abnormal, the host sends normally, the slave cannot reply, and the slave can still debug the serial port separately, and it is found that unknown data triggered the reception interrupt after the slave is turned on, and it cannot be triggered in the future.
 2: The host is turned on first, and the slave is turned on later, and the communication is normal.
 3. Turn on the slave first and then turn on the host later, and communication is abnormal.

 In case 13, the SCI interrupt will never enter the interrupt after successfully entering the interrupt once, but the program does not run away, and the main loop and AD control interrupts are still running normally, and they are also running normally.  Looking at the SCI register, I found that when the host is powered on but the command is not actively sent, several bytes of data will be inexplicably added to the slave receiver.  After the error byte data appears, the SCI reception interrupt can no longer be entered. At the same time, the SCI receiver error flag of the 3rd bit (OE) overflow error flag, the 4th bit (FE) frame error flag and the 7th bit (RX ERROR, the value is the 2nd, 3rd bit register or operation result) of the SCI receiver error flag is 1.  Under normal circumstances, all three registers should be 0.
 Based on this, it is determined that the SCI has received an error, resulting in the SCI receiving interruption.  After reviewing the relevant information, I found that to solve the problem of error flag position caused by error flag position, a complete SW RESET (the 5th bit of (SCICTL1)) needs to be performed.

Solution:
1. Enable SCI reception error interrupt
2. When an SCI reception error occurs, the SCI reception interrupt will be entered, and determine whether the flag bit RX ERROR is set (if the SCI reception error causes an entry interrupt, the RX ERROR is naturally 1)
3. When RX ERROR is set, execute a complete SW RESET and exit the interrupt
Analysis of error causes:
Through the above 3 steps, the program can continue to enter the SCI reception interrupt normally, and SCI communication will return to normal. Since the communication program has not been changed, it is considered that it is an error caused by environmental electromagnetic interference when powered on.

Attached the modified code

void Init_Scia(void)
 {
     EALLOW;
     SysCtrlRegs. = 1; // SCI-A
     EDIS;

      =0x0007; // 1 stop bit, No loopback
                                    // No parity, 8 char bits,
                                    // async mode, idle-line protocol
     SciaRegs. =0x0003; // enable TX, RX, internal SCICLK,
                                    // Disable RX ERR, SLEEP, TXWAKE
     SciaRegs. =0x0003;
     SciaRegs. =0;
     SciaRegs. =1;
     SciaRegs.=1; //Enable Error Receive Interrupt
         =0x0000;
         =SCI_PRD;
      =0; // disable loop back
     SciaRegs. =0x0023; // Relinquish SCI from Reset
 }

interrupt void SCIRXINTB_ISR(void) // SCI-B interrupt
 {

     if( == 1) //SW RESET
     {
            ScibRegs. = 0;
            DELAY_US(1000);
            ScibRegs. = 1;
     }


 // Normal SCI interrupt function
 // ...
 // ...
 // ...

     .ACK9 = 1;
     EINT;
 }