program prom by the fpga

Hi,

I am trying to program the configuration prom (xcf16p) through dedicated pins of my fpga. i.e I connect some GPIO of my fpga to the JTAG inputs of the prom, and try to load a new configuration to the prom. I do the configuration by impementing the jtag command in the .svf file produced by iMPACT.

It does not work, and my fpga is erased even when i am only trying to read the IDCODE.

Although I put a logic analyzer of the prom jtag input and compared the captured waveforms of

1. jtag programming by iMPACT (that works)
2. programming by my GPIO (.svf file - does not work)

and the waveforms look the same (till the point my fpga is erased ....)

ThankX NAHUM