If both the Parallel JTAG Download Cable, and the Xchecker Serial Download Cable are connected to the machine, only the Parallel Cable will be seen by the computer, even if the Xchecker cable has power.
ソリューション
If you wish to use the Xchecker Cable for programming, be sure that the Parallel JTAG Cable is disconnected from the computer BEFORE invoking JTAG Programmer.