When you connect two computers via a COM port connection, and use HyperTerminal to transfer hexadecimal data, incorrect data may be sent.
The behavior occurs because HyperTerminal uses Auto detect by default, which causes the high-order bit of every odd byte to be changed, starting with the third byte.
If you were sending FF FF FF FF FF FF FF from the keyboard, or from a file, Auto detect would cause FF FF 7F FF 7F FF 7F to be sent.
To workaround this behavior, turn off Auto detect:
1. Open the HyperTerminal application from the Start menus Accessories / Communications folder.
2. Configure the COM port connection that you desire, changing Emulation.
3 Use the Call menu to Call.
4. Note that the HyperTerminal Status line reads Auto detect Auto detect.
5. Use the Call menu to Disconnect.
6. The Status line should now read Auto detect <Your Emulation Setting>.
7. On the Call menu, press Call.