26 May
2011
26 May
'11
7:01 p.m.
You know, it all depends on the person. Personally, I call the logic
analyzer the "tool of last resort" or "the dreaded logic analyzer".
When
Well, yes, I guess it is, in that you do the obvious checks (power supply
:-:), etc first, and maybe use a logic probe to see if anything is
obviously wrong (like one bus line stuck when all the others are changing.
But for digital troubleshooting, I grab the logic analyser next. Most of
the itme I need at least 8 and often more input channels. I can't afford
a DSO with that many inputs :-)
Of course it does depend on what I am working on. A logic analyser is not
a lot of help in repairing analogue stuff like SMPUs and (most) monitors.
you need it, you need it and nothing else will do.
But often you can get a
long way with a 'scope and a logic probe (in the ancient days when strobes
were easily accessible).
These are the 'ancient days' aren't they? This is classiccmp, and I am
talking about repaurubg classic computers.
When you're debugging a 32 bit bus and you've got probes hanging all over
the place, then you know you are deep in hell --- one of the circles that
Dante didn't describe.
I think it would be very difficult to repair an HP9800 machine or even an
HP9866 thermal printe (to name 2 ofd the devices that have been across my
bench recently) without a logic analyser. You might get lucky and find a
signal that's obviously way off, but much of the time you need to trace
the sequence of the microcode or control state machine (which are much
the same thing, actually...)
-tony