Re: C64 DMA

From: Marko Mäkelä (
Date: 1999-11-17 13:09:40

On Wed, 17 Nov 1999, COPLIN, Nicholas. wrote:

> the questions I have are:
> 1) what memory map does the DMA see? is it the one defined by the 6510 port
> or are the port lines also Z-stated?

>From my somewhat limited experience with the REU, it is the one defined by
the 6510.

> 2) if the mem-map is still the 6510 view, then do write throughs to under
> the ROM still write to RAM

I think so, yes.  The DMA device simply replaces the processor.

> 3) how does one DMA to write to the 6510 ports 0x0000 and 0x0001???

One doesn't.  It's also difficult to write to the memory locations 0 and 1
with the 6510, but it's possible and I've done it.

> 4) can the IRQ /NMI lines be "read" from the expansion port or are they
> buffered only for generating requests? they look unbuffered to me.....

Yes, they are bidirectional in that sense.

> The contents of this email (including any attachments) may be 
> privileged and confidential.

Does this mean that your company is going to develop an accelerator
cartridge for the C64? :-)


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