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Altera_Forum's avatar
Altera_Forum
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14 years ago

strange speed for DMA transfer

Hi guys, I got my DMA transfer running on a DE2-115 board, from off-chip SDRAM to off-chip SRAM. The data to transfer was 0.5M 32-bit word type, just enough to fill the 2MB SRAM on the board...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

Yes at most the DMA will transfer one world per clock cycle, so yes there is something strange.

What DMA did you use? Some DMAs have a limit on the number of words they can transfer. Are you sure that all 2Mb were actually transferred?

Are you sure that you wait until the DMA transfer is finished before triggering the performance timer? If set in asynchronous mode, the function that starts the DMA transfer will return before the transfer is actually complete.