Posted By
MMS
on 2015-01-03
18:08:15
 |  Re: World of Commodore 2014 pictures, video, reports
OK, a little OFF:
you are probably right: the RDY and AEC inputs used by the existing Z80 cartridge, and NMI not, though some people think that's why the z80 cartridge was a flop (and too slow). AEC input we also have, but we seems do not have the ReaDY pin on the extension port. (So you cannot command to halt the processor temporarily).
So I was wrong with NMI.
DMA: if you see a memory address just with the gfx data, and it is directly loaded from an external device, for me it is a direct access.
They did not use any Plus/4 routine or CPU for the memory loading, but accessing and writing it directly.
OK, not the same or as flexible as the Intel's DMA, but rather similar, if you think twice.
Maybe closest to the "cycle stealing" DMA method, as the CPU should wait with the "ROM" reading till the external device stopped the writing of the "ROM".
"A DMA közvetlen adatátvitelt eredményez a memória és az I/O készülék között, a CPU igénybevétele nélkül. Igy a periferia közvetlen memória-hozzáféréssel rendelkezik."
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