RE: [N8VEM-S100:5426] Re: Getting to know your logic analyzer

I don't think mine has a 5V input, but just the same, don't connect it, only connect the ground between the two units and all the data lines. The analyzer gets it's power from the USB. Seems like a lot of work to extend all those wires, I recommend you just buy a longer USB cable or extension, be sure the USB cable is USB 2.0. An IC clip is a good idea.

Sample rate, I would choose the highest possible. This will give you the finest resolution when looking at the signals. If you are timing slow circuits over a long period of time, I would say that's the only time I would use the slower sampling rate. It goes without say that the higher sampling rate takes more memory, but memory is cheap. If you choose a lower sampling rate, you might miss a glitch pulse.

J.

Date: Wed, 22 Oct 2014 15:02:32 -0700
From: ilv...@gmail.com
To: n8vem...@googlegroups.com
Subject: Re: [N8VEM-S100:5426] Re: Getting to know your logic analyzer

I broke out my N8VEM Zeta SBC and got the logic analyzer working.
Was able to fire it up and sample address and data lines. Starting to get
the hang of it but still have much to learn.

I only have six inches or so for my probe cable. I'd like to build a longer
cable for the pin grippers. I'm pretty sure we want this as short as possible.
Any ideas what would be a reasonable length? Can I go to 18"-24" ?

The other option is to get an extension USB cable.

A couple operational questions:

1) Do you have to hook up the +5VDC? Seems to work fine without it
2) When I'm capturing samples do I need to select the exact MHz Sample rate (1,2,4,8,12,etc)?
If running a 6Mhz system would 8Mhz be best choice?

On 10/21/14 02:09 PM, nbreeden wrote:

Yes, your right, I fat fingered it. :)
-N

The 7490 should roll back to 0000 after 1001. The 1010 code should reset the counter, I wonder if the output goes to 1010 if even for a few nano seconds while the flip flops are resetting? Or would the propagation delay of the output gates inside the chip prevent the 1010 code from reaching the outputs?

Date: Tue, 21 Oct 2014 10:23:29 -0700
From: nbr...@me.com
To: n8ve...@googlegroups.com
Subject: [N8VEM-S100:5412] Re: Getting to know your logic analyzer

I would be tempted to use a 555 to drive a 7490 (or other counter) then to look at the counter outputs as well as the 555 clock. If it's a decade counter you would see a binary 0000 to 1010 then back to 0000 on it's outputs; this would be something more interesting to look at. You could set up various triggers to get a feel for how a trigger affects the samples; look at different sample depths etc.

The more you understand the logic analyzer (including it's limitations) the better you will be able to use it.

Mostly though make sure you're having fun with it as you learn how to use it. :)

-Neil

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Don Caprio
ilv...@gmail.com

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