some virtexII clock pads are useless??

For test my fpga clock, I input a clock throuth one of the dedicated clock pad, and output it from a general I/O. From the oscillograph, I found some clock pads can give the correct signal, and the same clock input the other clock pads only have the '1' output.

p.s. I use the same vhdl code as follows: clkin-->ibufg-->clkout. Just differences in assign clock pins.

Any comments would be appreciated! thank you in advance!

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Here's a suggestion, in the V2 datasheet it says that "As long as the presently selected clock is High, any level change of S has no effect .". Is that your problem? Cheers, Syms.

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No, Symon.

I am afraid not, my problem is a real problem. It's something very simple and fundamental. I am switching between the two clocks when I loop one data path to another.

But thanks, appreciate it. Can you think of anything else?


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Vladislav Muravin

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