backspace shows ^? in serial communication

[s m]

hello all,

i have problem with backspace in freebsd 8.2. when i run a serial program to communicate via a serial port to the other system, backspace shows ^? in opened terminal. 
i use termios and fcntl to open, read, write and close serial port. i set erase and erase2 for ttyu2(my serial port) but backspace shows ^? yet.

any body knows what i'm doing wrong? just erase and erase2 should be set to backspace works correctly or any other options should be set?

any hints or comments are really appreciated.
nada