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This is the original DE2 with EP2C35. I did take a measure at voltages and they seem to be ok, although I can't do any real measurements due to lack of proper scope. What I also now tested was that I changed the VGA PLL to use the 27MHz oscillator as source. I still have jitter, although less than before. So the problem might be elsewhere (some signal termination?). I really hope the FPGA is not faulty.
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I'm not sure that 27MHz is the correct frequency for VGA. For example, take a look at
http://en.wikipedia.org/wiki/crystal_oscillator_frequencies Scroll down to 27.0MHz and you'll see that it is the reference frequency for NTSC/PAL, but scroll down a little further and you'll see that 28.322MHz is a VGA frequency.
Just because Terasic put a 27MHz clock on the board means it is "correct" for all applications. It may be that they expect you to use a PLL to configure the VGA interface.
You might want to do a little searching to see what other VGA examples exist for this board. Hamblen has a book and examples ...
http://users.ece.gatech.edu/~hamblen/de2/ Cheers,
Dave
Honored Contributor
