Receiving bad data from FIFO with DMA transfer

Altera_Forum · ‎12-05-2005

Hi to everyone,

i have some problems with the FIFO and reading DMA transactions.

After the transaction, and i dumped the data on the screen. At the very beginning i find some data (2 or words), which doesn't belong to the data i put into the FIFO. Futhermore on several position a single datum is missing and the very next datum has been reading twice.

If readout the FIFO with CPU (readl(...)) all is fine, so the data in the FIFO is OK.

Any ideas?

Thanks a lot

Altera_Forum · ‎12-05-2005

In SOPC, check that your avalon switch fabric is properly connected to your DMA port.

Not sure if this is your problem, but its a common thing to forget when using DMA:

henning

Altera_Forum · ‎12-06-2005

> I have some problems with the FIFO and reading DMA transactions.

Have you check for interference with the cache ? (if you have one)

If you have cache on Data, there are precautions to take to ensure the consistency of the external memory.

Hope this helps,

Bert

Altera_Forum · ‎12-06-2005

Hello Henning, hello Bert.

First of all i like to thank you for your ideas.

<div class='quotetop'>QUOTE </div>

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>If you have cache on Data, there are precautions to take to ensure the consistency of the external memory<[/b]

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i'm using a Nios/f core. To check if it's a cache issue i downgraded the core and removed the cache. the error remains.

<div class='quotetop'>QUOTE </div>

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In SOPC, check that your avalon switch fabric is properly connected to your DMA port.[/b]

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I will go after the connections (again and again :-)).

________

Meanwhile i verified that Memory is OK: I made a testpattern, which i copy from onchip ram to SDRAM and back, and from SDRAM to SDRAM.

Hopefully someone else has hint or better a solution.

Are there some known issues about configurations, which should be avoided.

I will check everything step by step...

Thanks

Helmar

Altera_Forum · ‎12-06-2005

Problem solved...

the problem isn't FIFO. It seems that it is an "electrical" problem. so far it seems to work now.

thanks everyone for trying to help me out.

Best Regards

Helmar