haks for the quick response.
I didnt connected anything else to the PGC/PGD.
it is connected directly.
The chip I use is pic18lf2455.
furthermore, after promgraming the chip on release state (microchip board), the code run successfully in my own board. (this is how I know that the clk and the other enviorment is working well).
but when i tried to program on debug state on the microchip board, it didnt connected to my own board with he following error : ICDWarn0020: Invalid target device id (expected=0x93, read=0x01)
I did connected a reset button (switch) to the MCLR.
it is connected with two resistors as mentioned in the attached image.
(R1=10Kohn, R2=10ohm)
thanks again for helping me in this issue.
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by the way the board i'm using is
picdem 2 plus.