SPI decoding and Chip Select

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itooo
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Posts: 0
Joined: Thu May 15, 2014 12:11 pm

SPI decoding and Chip Select

Post by itooo » Thu May 15, 2014 12:25 pm

Hello,

it seems the Chip Select is not taken into account when decoding SPI data, see this capture :
spi-cs.png


- Blue is MOSI
- Red is CS
- Green is SCK
- Gold is MISO

Taking a look at ~50us we can see CS is deasserted during a byte cycle (only 2 clock cycles have been done when CS is deasserted).
The decoding engine should abort when CS is released and start over when it is asserted again.
What we see here is the decoding engine takes the 6 first next clock cycles and merges them to the unfinnished previous word to build the next byte. Thus all the decoded data is shifted after this event.

Here are my settings :
spi-settings.png


Did I do something wrong ?

Regards,
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Hitesh
Site Admin
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Posts: 2793
Joined: Tue May 31, 2011 3:43 pm
Location: St. Neots, Cambridgeshire

Re: SPI decoding and Chip Select

Post by Hitesh » Wed May 21, 2014 2:07 pm

Hi itooo,

Thank you for highlighting this issue - there is a bug in the software which will be investigated and fixed.

Regards,
Hitesh

Technical Support Engineer

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