SPI Decode Error

Logic 2 Software
1

Hi,

I am looking at the SPI transactions between a AD9838 and the AD programming board.

The SPI decode is set to CPOL = 1 and CPHA = 1

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Whilst it appears to be technically compliant with scheme the SPI decode seems to miss the first falling edge after the enable line goes low and so gets the data wrong.

ad9838_program.sal (4.3 KB)

What would be the quickest way to get it decoding properly?

Thank you

Bob

2

The SPI analyzer thinks the rising edges on the clock signal are the active edges and has placed little up arrows on them to indicate this. However the MOSI line changes on the clock edge so most likely the clock active edge is falling.

3

Well this is an embarrassing case of blindly following a datasheet and not playing around with the settings enough.

I set them to the opposite of the datasheet and now it works.

Thanks

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