code=filename.txt]include <Philips8xC31-51-80C51Fx-80C51Rx+.h>
#include <standard.h>
#define PORT1 P1 // P1 recieves the ADC data and transfers it to serial port //
unsigned char mybyte ; //intermediate variable//
void serial_send(unsigned char mybyte ) ;
void main (void)
{ TMOD = 0x20;
SCON = 0x50;
TH1 = 0xFD;
TR1 = 1 ;
TI = 0 ;
while(1)
{ mybyte = PORT1 ; // from port 1 to mybyte variable //
serial_send(mybyte) ;
}
}
void serial_send(unsigned char mybyte)
{ SBUF = mybyte ;
while(TI) <------- Shouldn't there be a semi-colon?
TI = 0 ;
}
  Also, how come you dont have a specific interrupt that the compiler understands.... like in KEIL here is an example:

void it_UART(void) interrupt IRQ_UART // shows the interrupt and IRQ_UART is the number given in the .h file


{


	if(RI)						// If reception occurs


	{


		RI = 0;							// Clear reception flag for next receptoin


		if (UART_INDEX < MAX_UART_BUFF)


		{


			UART_DATA[UART_INDEX] = SBUF;	// Read receive data


			UART_INDEX++;


		}


		else


		{


			SIOERROR = 1;


		}


	}


	else


	{


		TI = 0;				// If emission occured, clear emission flag


		CLRTI = 1;


	}


}
 

On top of that do you have your baud set properly? Which is highly dependent on what processor youre using and this isnt copiable.

void UART_Init(void)


{


	Set_uart_x1_mode();	// UART is in X1 Mode


	SCON = 0x50; 		// UART in mode 1 (8 bit), REN = 1 (ENABLE RECEPTION)


	BDRCON &= 0xEE;		// BRR = 0 (BAUD RATE GENERATOR NOT RUNNING); SRC = 0 (Set if using MODE1 for IBRG);


	BDRCON |= 0x0C;		// TBCK = 1 (USE IBRG); RBCK = 1 (USE IBRG); SPD = 1 (USED TO CALC BAUD);


	PCON |= 0x80;		// SMOD1 = 1 (USED TO CALC BAUD), SMOD0 = 0 (USED TO SELECT SM0)


	BRL = 0xF3;		// 19200 Bds with 48MHz OSCILLATOR, X1 mode, SPD = 0, SMOD1 = 1


	ES = 1;			// Enable Serial Interrupt


	BDRCON |= 0x10;		// Baud rate generator run


}