Logic Analyzer Recommendations

A logic analyser is basically an oscilloscope for digital signals. They have a number of input chanels (anything from 3 to over 100) that you connect to various points of the device under test. The logic state of all those points is recorded every so often (say every 50 ns), the time being selectable of course. You can then display those recorded states as a timing diagram, and sometimes as a table of values (you 'tell' the analyser that channels 0-15 are to be displayed as a 4 digit hex number, that channels 16 to 23 as a 2 digit hex number, etc). Some analysers even let you load a disassembler program for a particular processor at which point you can display the result as a dissassembly listing [1] You can set the analyser to trigger on a particular combination of inputs (that's the simplest case, many analysers have very complex trigger modes) and then either start recording when you get the trigger, stop recording when you get the trigger, or carry one recording for about half the analysers memory size on the trigger (so the trigger event occurs aproximately in the middle of the data that's been recorded). As to why you'd want one, well, if you have a complex digital circuit, and you need to see what's going on (either because you've just designed it and need to find out what mistake you've made this time, or because it's stopped working), a logic analyser will let you look at all the signals in said circuit at once and display the relationship between them. [1] Personally, I think this is a somewhat useless feature. Of much more use is the ability to link the analyser to a computer (e.g. via GPIB, RS232 or these days I guess USB) and transfer the recorded data. Then you can attack it with any program you like. -tony