Honored Contributor
Honored ContributorHello Dan,
that sounds plausible to me, although I don't know what's happening in detail. The behaviour most likely depends strongly on your acquisition clock. SignalTap hasn't a glitch detector like e. g. a logic analysator or a digital oscilloscope. It does all signal processing in synchronous logic, being constrained by the same setup and hold requirements as your design under test. Particularly, an edge trigger isn't a FF clocked by the signal, it's a synchronous edge detector. If signal duration is too short related to your acquisition clock, SignalTap could miss it. I don't know, if there have been changes to trigger logic that may affect behavior with short pulses. It can also be an effect of timing differences from place and route. As a general rule, I wouldn't expect pulses shorter than a period of sampling clock to trigger SignalTap reliable. Regards, Frank
