AnsweredAssumed Answered

SPI Documentation Error - protocol clock

Question asked by Peter McLean on Oct 25, 2016
Latest reply on Oct 27, 2016 by Peter McLean

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?

Outcomes