|Re: Whatever happened to the "Logic Dart" HP product?|
Message #3 Posted by Tony Duell (UK) on 5 Aug 2003, 4:26 p.m.,
in response to message #2 by Ellis Easley
Indeed I do have a LogicDart, and several of my friends (who played with mine) bought one too. So it certainly shipped.
It is one of those typically HP products -- an excellent tool that was somewhat badly marketted. The most useful mode is 'Investigate' In that mode, you put probe 1 on a point in your circuit. The unit displays the average DC voltage at that point (great for checking power lines) and the freqeuncy (done by counting the number of crossings ofa threshold in one second or something). So far it doesn't sound like it does more than a good DMM, but if you now press the appropriate button, it records the logic waveform (high, low, undefined, with user-selectable thresholds) at that point.
So it's great for distiguishing between clock waveforms (close to 1:1 Mark:Space ration, and regular) from sync pulses (more extreme Mark:Space ratio, but still regular) from data lines (not regular). Much of my HP classic-series calculator investigations were done using this mode.
There's also a 3 channel logic analyser mode. 3 channels doesn't sound like much, and indeed I am sometimes gald of my larger benchtop logic analyser. But 3 channels will let you look at most handshake sequences, or clock and data lines, or...
One great feature is the fact that it records each signals as high, low, or undefinded. This is very useful for picking up illegal levels either due to shorts between signals or faulty chips. This saved me a lot of time when sorting out my 98x0 machines, which had a number of 74Hxx chips that didn't pull high properly.
The threshold settings will even (just about) let you look at the flip-flops in an HP9100...
I guess I can sum up by saying that it's the first instrument I go for when investigating an unknown digital circuit, or when testing one of my own designs. Sure I sometimes need the 'scope or the bigger logic analyser, but the LogicDart often gives enough clues on its own, or at least it tells me where to use the larger instruments.