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
> 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.)
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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