Thanks for your reply ,
I am using .pof configuration file. I think the board doesnt support other configuration like .sof
I will try reducing JTAG frequency.
May i ask you one question? Why do we need to reduce the clk freq.?
Sometime the signal integrity and timing prevents operating at 24 MHz. Thus, the optimum recommended value is 6 MHz (default value).
In addition, the TCK frequency cannot change using the USB-Blaster download cable.