SPI Documentation Error - protocol clock

[pmcl]

Hi All,

I'm looking at the K70 Reference Manual, Chapter 54, SPI.

In the section on the SPIx-CTARn, pages 1815 onwards, it mentions 1/fp in various formula.

I'm trying to set up a "Delay After Transfer". According to page 1818:

"The Delay after Transfer is a multiple of the protocol clock period, and it is computed according to the following equation:

t(DT) = 1/fp x PDT x DT"

This means that 1/fp is the protocol period, and fp is meant to stand for the protocol frequency (bit rate).

However, upon testing, it appears that the delay seems to be a multiple of the module clock, not the protocol clock. I'm using a protocol clock of 1 MHz and a module clock of 25 MHz, and the delay is exactly 25 times smaller than the formula.

Is the documentation wrong? Should it say "module clock" rather than "protocol clock" and therefore all the other formulas/wording needs to change too? Is this a common problem across the Kinetis family?

[cutworth]

Hi Peter,

Yes, this is not that clear when using fp to represent module clock. This has been fixed with other Kinetis document where it is changed to fsys. 

Hao

[pmcl]

Hi Hao,

Thanks for the quick response.

It's not just the "fp" that's the problem - the descriptions explicitly mention "protocol clock", not "module clock", so the wording that goes with fp needs to change.

Anyway, I was looking for a way to point out the error to someone in NXP - didn't see a direct link to "report an error", so I posted on the forum.

Thanks for your help.

PMcL

[cutworth]

Hi Peter,

Thanks for reporting the documentation error. I will let associated person know this.

melissah‌ Could you help look at this reported documentation issue for K70 SPI module?

Hao

[melissa_hunter · Accepted solution]

Hi Peter,

Yes, thank you for reporting the issue. I entered in a PDM ticket against the manual requesting to have this fixed. The manual did get an update somewhat recently, so I doubt the documentation team will get to this any time soon.

If you need the updated documentation, let me know and I'll see what I can do to expedite.

Regards,

Melissa

[pmcl]

Hi Melissa,

I'm fine with the current documentation - now that I know about the error.

Thanks for your assistance.

Regards,

PMcL