I try to write program about Serial interface but it invalid. Can you recommend I abiut this?. Are my source code correct?. this program I try to send "0" #include <reg51.h> sbit PLLCON = 0xD7; int N,i,x0; float dat = 0; void main(void) { /**********Define UART variable***************/ SCON = 0x40; //Serial mode1-->8-bits UART PCON = 0x80; //SMOD = 1 PLLCON = 0x50; TMOD = 0x20; //Timer Mode2 8-bit auto-reload TR1 = 1; //set bit TR1 --> Timer1 Run TH1 = -9; //Baud rate = 9600 TL1 = -9; TI = 0; /*********************************************/ dat = 0x30; while(1) { TI = 0; SBUF = dat; while (~TI) TI = 0; } }