Serial port Communication PC and AT89C52 ( continuted )

Here was my plan to realize the communication between PC and AT89C52, Both of them are set to 2400 (baud rate), N, 8, 1.
1. I have shortened pin 2 and pin 3 of RS-232 attached to PC. When my pc was sending out DATA, at the same time it can receive this DATA. After doing this, I found my PC can correctly receive the DATA just sent out.
2. The following is my C51 code. After receiving the incoming data, I want to show that data by LED connected to P1 port.
I thought my C51 code should be wrong, but I really have no idea……Please help me….
Sincere Thanks in advance.

unsigned char ISRIN;
unsigned char ISROUT;
unsigned char SERIALISRIN;
void DELAY ();
void INI_SERIAL();
unsigned char RECE_SERIAL ();

void main ()
{
   unsigned char DATD;
   P1 = 0xff;
   INI_SERIAL();
   While(1) {
        if (ISRIN ) {
           ISRIN = 0;
           DATD = RECE_SERIAL ();
        }
   }
}

void SERIAL_ISR ( ) interrupt 4 using 1 (
      if ( TI ) {
         TI = 0 ;
         ISROUT = 1;
      }
      if ( RI ) {
         RI = 0;
         ISRIN = 1;
      }
}

void INI_SERIAL() {
      EA = 0;
      T2CON = 0x34;
      RCAP2L = 0x64;
      RCAP2H = 0xff;
      TL2 = 0x64;
      TH2 = 0xff;
      SCON= 0x50;
      TI = 0;
      RI = 0;
      TR2 = 1;
      ES= 1;
      EA =1;
}
unsigned char RECE_SERIAL () {
unsigned char DAT;

      P1 = SBUF;
      DAT = P1;
      DELAY ();
      P1 = 0xff;
      return DAT;
} 

By the way,how to select AT89C52 Timer 2 Serial Clock Divisor? right now, I am sure my MCU is working correctly for receiving and sending out the data ( I did this under a friend's suggestion ). SO I thought the Serial Clock Divisor of AT89C52 is wrong.

Would you help me to check it?

Thank you.