measure the length in the SignalTap in Quartus 18.1
My reference clock in the signal configuration is 100 Mhz which it is 10ns, and I got one clock edge to edge which SInalTap shows +8 within different ruler. Is it correct that I got 125Mhz? Can you verify it?
I assumed the different ruler that you referring to is the time bar? Locate on top of the 'Data' tab. Please help to clarify if not.
SignalTap uses the clock inside the FPGA to do the data sampling. As far as I know, there's no independent timebase that you can use as a reference to measure time intervals or frequencies directly from SignalTap.
I suspect you may be seeing a different time scale due to the preset time scale from the previous project.
To correctly showed the time units, right-click on the time bar > Time Units > choose your reference units (e.g. 100 MHz or 10ns).
Hope it helps.
Thank you for your information. From scope and SignalTap measurement during experiment, SignalTap cannot get exactly frequency value, but it can get logic relationship with other signals. I original think it might perform same feature as Xilinx chipscope. This is why I have this question. As long as I know the difference and usage, I am fine for this issue. Please close this case. Thank you so much for your information.