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Query about DMA

nerd_emperor
nerd_emperor asked
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Last Modified: 2010-04-27
In theory , the processor only has to pass the base address of the bytes to move, the number
of bytes to move and the base address of the destination to the DMA controller, and it will
take care of the actual transfer while the processor does something else. However, Winn L.
Rosch writes in his excellent "Hardware Bible", that in practice the processor must not only
set up the transfer but also oversee it. Is this true? If so, what does it mean:
-the processor waites around?
-it double-checks to see whether the transfer is working properly?
-it waits for the end of the transfer?
-it looks out for error signals?

And if it does wait around, is it a software or hardware constraint (i.e does the program tell
the processor to wait before the end of the transfer or does the DMA controller/bus
controller/processor or other hardware device cause this?)

I would be very glad if you could help me resolve this small problem. Thanks
 
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Commented:
Thanks very much!!!

Author

Commented:
Understood, but why does he choose the word "oversee". As far as my knowledge of english goes, that implies some sort of supervisory function. The answer you gave would be more of a "hanging about" or "waiting".

Commented:
Dunno why he'd say "oversee". Maybe he meant in the larger context of setting it up for the next block request.
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