The most common cause for data displaying incorrectly when using a serial comms connection, is that the data format of TTWin3 hasn't been setup to match the host data format. By default TTWin3 uses 8N1 data format, this can be changed in the menu option found under Configure > Comms.

Another possible cause is that the baud rate of TTWin3 doesn't match your hosts baud rate. The TTWin3 baud rate is also set in Configure > Comms and by default is set to 9600bps.

After you have made the required changes to your Serial comms setup, you will need to save your session file if you want to keep your new settings, this is done by selecting Save from the File menu.