[En-Nut-Discussion] Remote DMA for RTL8019AS

HeltonGA at aol.com HeltonGA at aol.com
Tue Jan 6 04:27:44 CET 2004

What are the purpose for the remote DMA count registers (RBCR1:RBCR0) for the 
RealTek part ?

I assume that when the value in these DMA count registers reaches 0:0, then 
the DMA address registers are not incremented any more. Further read attempts 
would only read the value in the last DMA address. Is this correct ?

If I use a counter within the program (loaded from the packet header) to get 
bytes from the NIC ring buffer, then why do I need to load the DMA counter 
with a specific value ? Couldn't I just load the MSB of the DMA count with 0xFF 
(total count at least 0xFF00), then read the DMA port until I'm done ? If it's 
possible, it would save some code by not having to diddle the DMA count as 

In addition, is it possible set the DMA count to 0xFF00, set the DMA address 
to packet 1, read some bytes, decide that I don't like it, set the DMA address 
to packet 2 and continue reading ?

This is a lot of "what if's", but some insight into the working of the NIC 
chip would be helpful.

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