I am trying to use scanf function. After testing it successfully in simulator mode, I move to monitor mode to use it to input an integer number from serial window of debugger which is as PC terminal environment. It does not work as I want and the PC of program automatically set to 0000H, reset address. After considering, I found whenever I use getchar function (also use for scanf function), the serial window of monitor debugger always send the unwanted control character DC1 (0x11) to the target board. For the last time when I used the program MON51.EXE, I met this problem. I have to checked and discard manually this character from input string. I would like to ask anybody who met the same problem can show me the way to disable this function from debug environment.