Two newbie Chipscope questions

Jan 16, 2007 1 Replies
K

Hi,



I am new to using Chipscope, I've read the manual and lots of tutorials in the www and threads in this newsgroup.



Is there a way to see the "real" edges of my signals? All I got to see were these perfect rectangular edges that I see in the simulation, too. To find some glitching-related problems, wouldn't it be useful/necessary to see the actual edges that happen in the FPGA?



How can I trigger a change in a signal, i.e. I want to start "recording" my signals, when I push a button on my board?



Thanks in advance for any hints!



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B

Hi,

No. Chipscope is a logic analyzer, not an oscilloscope. It pretty much relies on your logic being synchronous to the clock that's being used to sample the data. Plus there are no GHz-bandwidth ADCs embedded in the FPGA that could be used to capture these "real" traces.

Unless you're doing something really esoteric in your design, such glitch-related problems will never arise. The tools take care of the timing closure for you, and the sub-micron designers at Xilinx take care of the low-level internal signal integrity issues and so on. So you really truly can work at the boolean-or-higher level of abstraction in complete safety (or your money back).

If you suspect you have duff signal integrity at the pins of your FPGA, then grab yourself a real scope and go to town (but Chipscope won't help you there).

Cheers,

-Ben-

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