DC debugging problem 3100 core

I’m a new user with DC. I begin with a simple program ‘controlled.c’.
After turning the power on, connecting the target, compile BIOS (till here everything is good), I Compile and run the program.

An error display “while debugging :Timeout while waiting for response from target”

I am connected with serial port (115200 baud rate)…

Thank you for your help.
:confused: