[51] Serial communication with 8052

#include <reg52.h>

sbit P3_4 = P3^4;
sbit P3_5 = P3^5;

void  RecDat(void)
{
    unsigned char dat;
    
    RI = 0;    // this is a flag set by hardware and cleared by software
    dat = SBUF;    // SBUF it's a 8 bit buffer that contains the 8 bit data received by uart
    P2 = 0xFF;     // i set ths port to this value to turn on the display

   if( dat == 'a' )
	 {
		P3_4 = 0; // turn on the correct led
		P3_5 = 1; // turn off the wrong led
	 } 
	 else 
	 {
		P3_4 = 1;    // turn off the correct led
		P3_5 = 0;    // turn on the wrong led
	 }
}

void InitSerial(void)   // Simply setting for UART and BaudRate MCU
{
    TMOD |= 0x20; // Timer 1 in mode 2 (auto reload)
    TL1 = 0xFD; // 9600 baud rate
    TH1 = 0xFD;
    SCON = 0x50; // Setup UART mode 2
    TR1 = 1; // Start Timer1 and UART
}

void main (void) {
        
    P2 = 0x00;
    
    InitSerial();

    while (1)
        {
        if (RI) { // if a receive the data by Serial RI it's setting by hardware to 1
            RecDat ();
        }
    }
}

if( dat == 'a')

if( dat == 0xFF )