scatter and gather configuration in eDMA in S32K144?

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scatter and gather configuration in eDMA in S32K144?

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shivamshankarg
Contributor III

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?

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lukaszadrapa
NXP TechSupport
NXP TechSupport

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.

pastedImage_3.png

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

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1,375 Views
lukaszadrapa
NXP TechSupport
NXP TechSupport

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.

pastedImage_3.png

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

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shivamshankarg
Contributor III

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.


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lukaszadrapa
NXP TechSupport
NXP TechSupport

Hi Shivam,

there are 16 DMA channels on S32K144:

pastedImage_1.png

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

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