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What SPI trial limitations ?

Question asked by aospan on Oct 12, 2012
Latest reply on Oct 16, 2012 by ksmith

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Hello,

I have requested "N5391B I²C and SPI Protocol Triggering and Decode for Infiniium scopes" trial 14-ay license. It works but I can't shrink memory depth in "Acquisition Setup" menu. Maximum allowed value is 10.25Mpts but I want to make longer sequence.
Is this trial license limitation or something else ?

P.S.
oscilloscope is MSO9404A with option500 (500 mpts memory).

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algoss Oct 12, 2012 6:41 AM
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This is a limitation in how much data can be processed in one "chunk" in the scope. This applies to all of the trigger and/or decode apps, with both trial and full licenses. It was an engineering decision, and is limited by the scope HW and SW architecture.

You don't indicate anything else about your setup, but if your data rate is slow, you can reduce your sample rate, which will increase the amount of time that gets processed. If your clock is 10MHz, for example, you can reduce your sample rate to 200MSa/sec, or maybe lower. A multiplier of 10 to 20 should be enough.

Experiment with this and report back, please.

Al
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- ksmith @ algoss on Oct 12, 2012 9:08 AM
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  Gotta disagree with Al a little.
  
  The 9000 scope should support up to the max memory for SPI (and other) decode trigger. This didn't used ot tbe the case.
  
  so...
  
  default the scope and try again
  OR
  update the scope software: [www.agilent.com/find/infiniium-sw]
  
  Of course, Al's point about lowering the SR is excellent.
  
  one could also use segmented memory (which is most useful if the packet lengths are constant)
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aospan Oct 15, 2012 12:58 AM
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Thanks for answers !

This is my mistake. Now I can assign 256mpts size (with demo SPI license). I'm setting up 4-wire SPI mode.
Analog sampling rate: 125M
Digital sampling rate: 50M
SPI clock about 10 Mhz.

Now I can record 2-3 seconds of SPI transfers ... it's ok for my goals :)
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- ksmith @ aospan on Oct 16, 2012 8:59 AM
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  with option 500, and all chs on, u shud be able to get 500 MPts/ch in "single" mode and 250 Mpts/ch while "running."
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What SPI trial limitations ?

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