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Altera_Forum's avatar
Altera_Forum
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14 years ago

DMA Transfer problem

Hi, I am trying to do a simple DMA mem to mem transfer as per the "Chap24: DMA controller core " example. I have been at this for almost a week now and it is still not working for me. Can you p...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

If you use the uncached malloc make sure you pass a pointer to the DMA that is masked with 0x7FFF_FFFF. Uncached pointers have the upper bit set which is the cache bypassing mechanism Nios II uses without an MMU. If you used regular malloc the worst that can happen is a cache coherency issue between the DMA and CPU, that wouldn't cause your waiting loop to get stuck.

I can't tell if your Qsys system is wired up correctly without seeing a screenshot of it.