I've done a program using the simulated serial port. My program has to communicate with a PC using the 232 interface, so I use the simulated serial port for the monitor, and the 232 interface for the program. The program works. The problem is when I burn the program in ROM, because I want it starts when I switch on the board. Then I erase the monitor program in the flash, and I burn my program in the external ROM. Then the communication 232 doesn't works. What is happening??. Here you can see my configuration of the serial port: S0BG = 0x0040; DP3 |= 0x0400; /* Set TXD for output */ DP3 &= ~0x0800; /* Set RXD for input */ P3 |= 0x0400; /* Set TXD high */ tx_restart = 1; /* Set restart flag */ S0CON = 0x8019; //8 bits, 2 stop, no parity S0RIC = 0x0076; //Interrupts RX S0TIC = 0x0075; //Interrupts TX S0TBIC = 0x0077;//Interrupts buffer TX The same program works from the RAM with monitor in ROM. I've tried using DAVE, but I haven't got any improvement. Can anybody help me? Thank you