On 07.10.14 09:14, Gene Heskett wrote: > But recognizing that clipping is something that generally comes from 60+ > years of using a scope that can show you that stuff. And that is > something a logic analyzer simply isn't capable of doing until the > condition actually forces a repeatable logic mistake. Thats maybe > .0000001% of the time even in bad designs that should never have been > shipped to the board house. But its often enough the gear will get a > reputation as being flaky out in the field. A slower scope won't show you > that regardless of the maker label on it.
Fortunately many of these small oscilloscope adaptors have two analogue channels in addition to 8 or 16 logic analyser channels. If the analogue channels have enough bandwidth, then they'll sniff out glitches and ringing, while the logic analyser channels see much less frequent use, to view timing relationships of a bunch of logic signals. The ability to trigger (analogue sweep included) on a bit pattern (with don't cares) on the logic lines, very nifty when you need it. And yes, experience can make a big difference. The scope probes have to be 100 MHz rated too, not just cheapy stuff. And that 3" lead on the probe's ground clip can cause ringing that wasn't there, if risetimes are short. For the tricky measurement above, I'll bet you use a little bit of tinned wire wrapped around the earth collar, bent to reach the nearest earth pin on the chip, in extremis. And, Viesturs, the little trimmer capacitor in the side of the probe initially needs to be tuned to remove false overshoot or undershoot on the trace, while the probe is held on a clean squarewave "calibration" signal. A good oscilloscope will include one of them on a pin on the frontpanel. (The BS325 has one, I read. My old BS310 doesn't.) Erik -- Reporter (to Mahatma Gandhi): Mr Gandhi, what do you think of Western Civilization? Gandhi: I think it would be a good idea. ------------------------------------------------------------------------------ Meet PCI DSS 3.0 Compliance Requirements with EventLog Analyzer Achieve PCI DSS 3.0 Compliant Status with Out-of-the-box PCI DSS Reports Are you Audit-Ready for PCI DSS 3.0 Compliance? Download White paper Comply to PCI DSS 3.0 Requirement 10 and 11.5 with EventLog Analyzer http://pubads.g.doubleclick.net/gampad/clk?id=154622311&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
