Question: Why is the MiniProg3 not able to program the board in XRES mode even though the board is powered externally?
XRES mode requires the board to be powered prior to starting the program. When the MinProg3 is used to program a board in XRES mode, it first checks for power at the pin connected to its VTARG pin. If that pin does not have power, it does not acquire the device.
If you are trying to program the CY3280-20xx6 kit using the MiniProg3 and an external power supply, the Vcc_prog pin at the ISSP header of the board is not powered, even though the device is getting power from the external supply. Make sure that the Vcc_prog pin is connected to the VCC pin using an external wire.
The MiniProg1 does not check for power prior to programming. It will try to program the device even if the VDD pin of the MiniProg1 is not powered externally.