scatter and gather configuration in eDMA in S32K144?

[shivamshankarg]

What is the benefit of scatter and gather configuration in eDMA in S32K144 if we compare to basic transfer?

there are 3 configuration i found in S32K-RM pdf.

1. basic transfer

2. scatter/ gather

3. peripheral DMA request

 actually i know the basic meaning of scatter and gather but i am not able to connect with eDMA?

[lukaszadrapa · Accepted solution]

Hi,

you can take a look at this application note:

https://www.nxp.com/docs/en/application-note/AN4147.pdf 

https://www.nxp.com/docs/en/application-note-software/AN4147SW.zip 

There's the same DMA module on MPC56xx devices.

In other words, this feature can help you in situation when you have only limited number of DMA descriptors but a lot of tasks to do. The same DMA channel can be used in a chain - once first data transfer (major loop) is completed, scatter-gather can be used to load another descriptor from RAM to the same channel and so on...

Regards,

Lukas

[shivamshankarg]

Hello lukaszadrapa‌ As written in 3.3 scatter gather features one DMA channel is allowed to use multiple transfer control descriptors so just want to ask how many transfer control descriptors is available in eDMA.

[lukaszadrapa]

Hi Shivam,

there are 16 DMA channels on S32K144:

Scatter-gather allows you to load endless number (theoretically, of course) of new descriptors to a channel. These new descriptors are supposed to be stored somewhere in flash or RAM and DMA engine will load them automatically when scatter-gather is enabled (you are just providing pointer to them).

Regards,

Lukas