Analyzer was Re: KIM-1 repair advice wanted

Scott Stevens 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>
> ---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.




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