Analyzer was Re: KIM-1 repair advice wanted
chenmel at earthlink.net
Fri Oct 7 19:24:09 CDT 2005
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>
> > First thing would be
> >to connect a logic analyzer to see if the CPU is still running
> >a programm in ROM or not.
> 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?
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
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