topic How to use DMA Scatter/Gather? in MPC5xxx

How to use DMA Scatter/Gather?

liujinhang — Wed, 22 Feb 2017 07:29:13 GMT

Dear All,

I want to use DMA Scatter/Gather function of MPC5444P,but some experiment phenomenon Confused me,the following is my DMA configurations information:

Problem phenomenon：when the major loop completed,the value of DMA_0.TCD[18].DLASTSGA.B.DLASTSGA was added to the DMA_0.TCD[18].DADDR.B.DADDR rather than the contents of TCD_SG1[] is loaded into the TCD register, then a DMA Destination Bus Error occurred.

Can anyone tell me how can i do to make the contents of TCD_SG1[] be loaded into the TCD register ?

here is the reference:http://cache.nxp.com/assets/documents/data/en/application-notes/AN4765.pdf?fromsite=zh-Hans

thanks very much!

Re: How to use DMA Scatter/Gather?

petervlna — Wed, 22 Feb 2017 13:16:54 GMT

Hi,

Do you have you scatter/gather descriptor 32bytes aligned in memory?

This is mandatory.

Peter

Re: How to use DMA Scatter/Gather?

liujinhang — Thu, 23 Feb 2017 02:10:07 GMT

It maybe the problem,The addresses of TCD_SG0[] and TCD_SG1[] are really not 32bytes aligned in memory . I misunderstood the meaning of "0-modulo-32-byte", thank you for your reminding!

but I do not know how to make the scatter/gather descriptor 32bytes aligned in memory. Can you give me an example?

thanks very much!

Re: How to use DMA Scatter/Gather?

liujinhang — Thu, 23 Feb 2017 02:59:12 GMT

hi, Peter

I did it ,thanks for your reply.

Best Wishes

Re: How to use DMA Scatter/Gather?

enes — Thu, 29 Mar 2018 20:24:33 GMT

Hi, we have same problem with scatter-gather method. Can u give more details about how to solve this problem.

Re: How to use DMA Scatter/Gather?

petervlna — Wed, 04 Apr 2018 06:44:19 GMT

Hi,

Just align your TCD in memory for 32bytes. Otherwise DMA will load incomplete or incorrect TCD.

PEter