Logic Analysers

Paul Berger phb.hfx at gmail.com
Fri Feb 3 11:09:04 CST 2017

On 2017-02-03 12:41 PM, Jon Elson wrote:
> On 02/03/2017 02:55 AM, Adrian Graham wrote:
>> Ah yes, sorry, I'm aware of that. What I meant in this specific case 
>> is that with 4 2764s right next to each other with a direct signal 
>> path between adjacent address and data pins that has a resistance of 
>> 0.5 ohms pin to pin surely I should be able to put a clip on each 
>> (for example) A4 address line and see the same pulse at all four 
>> channels? 
> Well, if the two logic analyzers were synched together, or you were 
> sampling at 100 MHz or above, then yes.
> But, if the logic analyzers are running too slow, sampling irregularly 
> (I have no trust in Chinese gizmos until PROVEN that they do it right) 
> you could get very different results.  Is there a clock on the 
> microprocessor that you can check?  Maybe something like a baud rate 
> clock or something that is at a few MHz.  See if that shows up as 
> totally regular square waves.  If not, then the LA may not be sampling 
> at a regular rate, or might have gaps while sending data to the PC.  
> I'm just suspicious of these units, given the results you report.
> (On my $130,000 Tektronix analyzer, I don't have to worry about such 
> stupid stuff, I know they got it right.  I paid less than $750 for it, 
> it will do 100 MHz on 288 synchronized channels, with a 128K record 
> length.  But, it is bigger than a big kitchen microwave, and much 
> noisier, too.)
> Jon
Same with my Agilent 16700B, however I current only have 192 channels 
available because I have two card slots occupied by digital scope 
cards.  The analyzer cards I have can do 110 MHz state or 500 MHz timing 
which more than meets my needs for the 30-40 year old computers I use it 
with.  One big advantage of a setup like this is one instrument can be 
used to trigger the other, for instance if I want to see what a signal 
really looks at at some point, I can use the logic analyzer to trigger 
the scope cards.  I also really like the external monitor on the 16700, 
its nice to work on a 19" display with a regular keyboard and mouse.  I 
have the 16700 set up with the back facing my work bench which gives me 
extra reach with the cable.  The only thing I need access to the front 
for is the power switch.   I do also have a analogue scope but I find 
myself using it less these days especially for digital circuits.
I also have a 16700A, 16600A, and a 16500C but they are rarely if ever 
used these days.


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