2 Jun
1999
2 Jun
'99
10:21 a.m.
ard(a)p850ug1.demon.co.uk (Tony Duell) wrote:
--snip--
Then I got a small (small enough to sit on top of any
part of a machine),
simple (but expensive!) logic analyzer.
I still don't like LA's because they can often hide real
signals. You see this nice squared wave that has been sampled
by the LA's input. The real live circuit may see something
else entirely.
What it hasn't told you is
that one input does nothing, and the gate is a simple inverter on the
other input. Yes, I've seen exactly that fault.
This is why I use my oscilloscope instead of a logic probe.
I can use more than one channel ( I don't consider single
channel 'scope to be useful for much more than patterns
in Sci-Fi movies ). Two channels is a minimum. While it
is true that non-repetitive patterns are hard to deal with,
in a computer I can often find a way to make the signal of
interest repetitive. In the rare case that I can't ( only
twice in 20 years of working with these things ), I rent
a logic analyzer.
IMHO
Dwight