Leaptronix PLA-2532 Logic Analyzer. Problems with SPI

Question

Hi,

I've just taken delivery of a Leaptronix PLA-2532 logic analyzer (SW ver 2.08). I'm finding the software very quirky and more than a little frustrating.

My biggest problem is with the SPI module and I wonder if someone can help me please.

I've set up a project with 4 lines; MOSI, MISO, SCLK and power. I go to the SPI module and tell what pins are which. When start decoding a valid SPI conversation, I get nothing. Part of the problem is connected to the SS line. The decoder seems to need some transitions on this lines. If I just connect SS to ground to imply the device is selected (it's the only device so there is no SS) then I get no output from the decoder. If I connect the SS input to either MOSI or MISO I get lots of data out but of course it's nonsense as the is no SS, the device is always selected.

Can anyone help me with this please?

Thanks,

Andy.

COMPACT · Answer

I hope you’ve already solved your problem.

It is not unusual for some SPI monitoring equipment to trigger only after the assertion of the /SS line. As for timing the /SS line is asserted first followed by SCLKs for the transaction and then negated.