AnsweredAssumed Answered

Repeated DMA request behavior

Question asked by SCOTT MILLER on Aug 17, 2018
Latest reply on Aug 20, 2018 by Jing Pan

I've read all of the documentation I can find on the Kinetis eDMA module (I'm specifically using a K22F part) but I can't find a good description of the hardware request handling.

 

My question is this:  Assuming the eDMA module is using round robin mode, if you have a DMA channel configured to fill the FIFO on a peripheral like the I2S/SAI module and a single minor loop doesn't fill the FIFO past the watermark, or if the SAI FIFO drains a byte during the transfer and the watermark isn't reached, is the new DMA request handled immediately by the channel with a new iteration, or does it wait until the round robin scan comes back around to that channel?

 

I'm attempting an unusual channel linking setup and I need to make sure the first channel always completes exactly one minor loop before each request on the second channel.

Outcomes