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Altera_Forum's avatar
Altera_Forum
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21 years ago

How to increase DMA fifo depth?

I need to increase the depth of the fifo in an Avalon dma. I thought I remembered reading about it, but I can't seem to find anything that jumps out at me in the .ptf. (dma v3.1, Nios v3.2) ...
Altera_Forum's avatar
Altera_Forum
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20 years ago

I worked with Ken Land on this issue quite some time ago (circa Nov 2004). After studying the problem for a while, I determined that the bug was not in the DMA, but rather in some user logic in Ken's system. At that time I felt that Ken accepted this result, and that the matter was closed.

Just for general info: the Avalon DMA has an internal FIFO to help improve throughput. It is true that the default size for this FIFO may not be large enough to provide optimal throughput, and the ptf assignment Ken mentioned can be used to bump up the size. It's also true that the size is rounded up to a power of two. You can read all about in the DMA generator program (em_dma.pm in the DMA component directory).

It is _not_ true that data is corrupted within the DMA when its FIFO becomes full.

Ken, if you're out there somewhere, would you care to step in and add your end-note?