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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

If you are using the DMA driver where you map a callback when the IRQ fires then maybe you are not measure the transfer time (just the setup time of the DMA). So normally with the driver the DMA is started and when the interrupt occurs a function (of your choosing) gets called when the DMA completes (IRQ fires).

In other words if you are just measuring the time it takes for alt_dma_txchan_send() and/or alt_dma_rxchan_prepare take to complete then you are not measuring the total transfer time since those are non-blocking calls.