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Message
From: Mark McDougall<markm@v...>
Date: Wed Sep 19 03:23:50 CEST 2007
Subject: [oc] WM DMA Transfer Size
bens@i... wrote:> I am having some trouble figuring out how to get the DMA to transfer
> its stated maximum total transfer size of 16k bytes. The TOT_SZ
> section of the register is 12 bits wide giving a maximum value of
> 4095. As far as I can tell, a value of 4095 will transfer only 4095
> words/16380 bytes and a value of 0 transfers nothing at all. Hopefully
> I have missed something obvious here, how do I get the core to
> transfer a 16k block?
I can't recall whether 0 transfers 0 or 4096 words... but you can use
linked descriptors to transfer two 8k-word blocks.
This appears to be a common and annoying limitation in other DMA engines
as well - the NIOS II DMA engine for example has the same 'feature'.
Regards,
--
Mark McDougall, Engineer
Virtual Logic Pty Ltd, <http://www.vl.com.au>
21-25 King St, Rockdale, 2216
Ph: +612-9599-3255 Fax: +612-9599-3266
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