Hi,
We have an eval board with a spartan FPGA and a 75MHz XTAL Within ourt design, we require an accurate 16MHz clock. It is not possible to generate this frequency using a single DCM, is it possible to chain 2 DCM's together to generate the 16MHz clock ?
(the obvious solution is to change the XTAL, but I'd like to know whether it is possible without changing the XTAL :-) )
Thanks for any feedback,
Steven
Howdy Steven,
Unfortunately you didn't provide enough information to really help you here. Which generation Spartan are you using? How accurate does the clock need to be? 16.00000MHz? Any duty cycle requirements? Jitter requirements?
There are five different generations of the Spartan. As you probably know, DLL's likely wouldn't help you much. S3 and newer with DCM's have CLKFX which might get you close, depending on your exact frequency and jitter requirements. Going the non-DCM route, I think a combinational output of multiple flip-flop dividers would allow you to generate this clock pretty accurately, but might cause jitter/duty cycle distortions.
Good luck,
Marc
Peter,
I do have the CLKFX option, so I can use your suggested solution.
Thanks for (both :-) ) replies,
Steven
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