On Fri, 7 Oct 2005 09:29:36 -0700 (PDT)
"Dwight K. Elvey" <dwight.elvey at amd.com> wrote:
From:
"Hans Franke" <Hans.Franke at siemens.com>
---snip---
First thing would be
to connect a logic analyzer to see if the CPU is still running
a programm in ROM or not.
Hi
What is it with logic analyzers. Why not just an
oscilloscope. In most cases, one can be farther along
with an 'oscope in finding what is wrong by the
time one can get an analyzer connected and setup.
I've only had one time that I ever needed an analyzer
and even that time, it didn't work well because
of the complexity of the problem ( design not failure ).
I'll admit that I've often thought of making one
of those address compare circuits to trigger the 'scope
but by the time I'd get serious, I'd found the problem.
Am I alone here or does everyone else think that an
analyzer is the ultimate tool?
Dwight
Or you can use the "Poor Man's Logic Analyzer" which is a pair of D/A
converters hooked to address/data lines and plugged into the appropriate
address lines. You hook the outputs of the DACs into an oscilloscope
configured as an X/Y display and adjust gain so that it makes a grid on
the screen. It shows you dynamically where the software is branching in
the memory map. If you use this method regularly, it can be a
'signature analyzer' of sorts. You'll get to know kind of dynamic
display to expect and/or you can even write short diagnostic programs to
'draw' specific patterns on the display. This sort of 'analyzer'
definitely shows wether a processor is in a 'lively' mode and running
around on the bus, or is stuck in a loop somewhere. If you want to be
fancy, you can latch the bus fed to the DAC with your chosen enable
signals.