Difference in Output of Simulator and Emulator

Dear All,

I am getting difference in output of Simulator and Emulator on using program Source

#include <reg51.H>
void SerTx(unsigned char);

void main(void)
{

int counter; TMOD = 0x20; TL1=0xFD; TH1 = 0xFD; SCON = 0x50;

TR1 =1; for(counter=0;counter<10;counter++)

{ SerTx('Y'); SerTx('E'); SerTx('S');

}

}

void SerTx(unsigned char x) { SBUF = x; while(!TI); TI=0;

}

In Simulator , it will show only 10 times 'YES' but in when flashed into a Micro - P89V51RD2, it keep on coming repeatedly.

Please explain