I am looking for how to measure the setup and hold time for signal.
Online it is showing lot of variation- sometime it took as 50% of data and 50% of clock and sometime it took 70% and 30%.

I am confusing that the cursor should be on 50-50% or 70-30% or 90-90%.

I need to validate RGMII, I2C and many more interface.
Attaching some pic for reference

50% of data-50% of clock


70% and 30% of data and clock

 

Use the manufacturer's methodology.

Are you trying to do go/no go testing for setup/hold times, or characterize?

 

Setup and hold times are not percentages. They are quoted in absolute times, usually in units of ns.

You need to measure the time difference from one transition to another transition.

If the rise time tr or fall time tf is reasonably consistent (order of ps) then it doesn't matter much if you measure the time difference from 50% to 50% or from 30% to 30%.

Going from 50% to 50% is good enough in most applications.

 

If you are trying to validate a circuit against a spec, then you need to use the methods and thresholds specified by the spec. If you are coming up with your own, then you get to do whatever you feel is reasonable, just document it in the spec.

 

Thanks a lot...I need to do it for characterization.