I troubleshooted PDA (Personal Digital Assistant) connection with PC via cable to PC serial port. So I adjusted the serial port setting. Then no matter how, both serial ports refuse to work. Removing the ports then reboot and recreating --- all in vain.
I tested with serial mouse, loopback serial plug and hyper terminal -- all no response.
The ports are solidly grouped with the parrallel port, they shouldn't have wiring fault.
Previously, when failed to get connnected to synchronize, the PDA could still auto switch on, but not now. Only, sometimes later on the hard disk on PC made sounds -- "tick..tick...tick...tick".
Parralel port still OK.