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Altera_Forum's avatar
Altera_Forum
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22 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
Icon for Honored Contributor rankHonored Contributor
22 years ago

Ok, I solved this.

I manually editted the .ptf file for my SOPC system and in the WIZARD_SCRIPT_ARGUMENTS section for the DMA module in question I added the following line

fifo_depth = "5";

This got rid of all errors! Awesome!

The default fifo_depth is 2, raising it to 5 gave the DMA engine enough timing leeway to work with the sdram.

This is pretty cool. It means on avg. I'm dma'ing one 32 word into sdram every 26ns.

I'm going to to some more testing on more loaded system and see if 5 is enough or if I need to increase it more.

Ken