Internal Capture of clock in FPGA

Hi @ all,

I am trying to use the Quartus SignalTap Analyzer.

Maybe someone can help me with my problem:

In the current state of my design test I have programmed my device. The receiving logic does not run yet because there is no incoming data traffic yet so that no IDLE-->Low transition is recognized. (Start of packet).

And yet I would like to know whether the PLL does generate the clocks correctly (PLL inclock:30MHz outclocks: c0 48MHz c1 : 90MHz, e0: 90MHz (external use)

Because of the fine package and the used board layers it is almost impossible to measure the clocks externally with an oszilloscope.

So the question is how to make the clocks visible with the SignalTap Analyzer. As I read in the application note it is said that clocks cannot be monitored.

But I cannot imagine that such a basic condition for a synchronous design cannot be captured.

What possibilities do I have ?

Thank you for your help.

Kind regards


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ALuPin a écrit: [...]

Hello The simple problem is that SignalTap uses on of these clocks to sample the data it monitors. You can't use a clock to sample itself, it stands to reason. The only way you can get around this is to generate a higher frequency clock to monitor your clocks but you may encounter performance problems because this clock will be quite fast.

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Reply to
Nicolas Matringe

I'm assuming there is some pin on your FPGA that you can get a scope on. How about patching your design to connect a FF to that pin and toggle the FF. That will give you a square wave that is half the frequency of your clock.

That's not good enough if you need to verify duty cycle and/or jitter in your real design, but it should give you a quick sanity check.

When doing the board layout, I always try to bring out a few spare pins to test points. Just for hacks like this.

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Reply to
Hal Murray

Simple! If you just need to be sure that the clocks are working, put a simple module in your FPGA that divides the clock by say, 16, and monitor it using the SignalTap! You won't know the duty cycle, but for that you really need to use an osciloscope!

Reply to
Arash Salarian

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