dma_memcpy with AM35x SDMA controller

Martin Stumpf

Hi,

I try to get a memcpy replacement via DMA controller running on AM35xx based on the example in chapter 7.5.2 of the reference manual. Unfortunately the example is not working on my system. For that reason I have some questions:

Do I need a request line for copying from DRAM to DRAM?
Is there a size limitation? I want to copy 700kb starting at 0x80000000 to some higher address.
Should I normally get an interrupt when doing a RAM to RAM transfer (example doesn't contain an interrupt handler)
Can I use any free DMA channel or are there restrictions?

Thanks,

Martin

over 10 years ago

0 Biser Gatchev-XID over 10 years ago

TI__Guru**** 393215 points

Hi,

What software are you running?

0 Martin Stumpf over 10 years ago in reply to Biser Gatchev-XID

Prodigy 20 points

We are using proprietary software but DMA is working for UART, SPI and MMC. So in general it is working. For RAM I tried to configure registers the same way as done for the other devices. Just not clear for me, with what to fill the request line.

0 JJD over 10 years ago in reply to Martin Stumpf

TI__Guru* 90745 points

Martin,
you don't necessarily need a request line unless you want to synchronize the DMA with some external event or peripheral event. You can kick off the DMA using software as well.
The size is dictated by element number (CEN) and frame size (CFN). You should be able to transfer that amount of data
You can set up an interrupt when transfer completes using IRQENABLE registers.
Any free DMA channel should be available to use.

Regards,
James

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dma_memcpy with AM35x SDMA controller