I'm running some USB verification testing at work, and the Agilent oscilloscope I'm working with returns a nice summary of pass/fail statistics along with a pretty eye diagram. Since the pass/fail is indicated within the scope, I don't need to do a ton of analysis on these diagrams.
I've looked at quite a few of these in the past few days and it's made me curious:In general, what separates a"good" eye diagrams from a"bad" one? In a lot of the tests I've run, the device failed, but the eye diagram looked very similar to one that passed.
I can understand a diagram where there are blatant crossings through the eye, but what other factors are taken into account when looking at these diagrams?