Re: AP-67 82C37 Application Note

HT-Lab wrote:
On May 24, 6:15 pm, "Wolfgang Kern" <spamt...@xxxxxxxxxx> wrote:
I am particular interested in how to add a page register for
the memory-to-memory transfer option,
I'd add one (three for 32 bit) HC374 or similar to it.

What I am after is how to select the latches. During normal IO-2-
memory transfer I can use the DACK signals as latch enables, however,
for memory-2-memory DACK0/1 are not asserted. The only indication that
a memory-2-memory transfer is in progress is that AEN is asserted but
none of the DACK signals. I can use this to select 1 latch/page
register but I need one for both the source and destination.

I actually remember this, from about 1982/83:

If your hw is compatible with the original IBM PC, then the mem-to-mem DMA feature is intentionally disabled! :-(

I don't remember what they used that port/feature for, but I do remember looking into it to be able to setup the DMA engine to transfer data from a RAM buffer and into the screen frame buffer.

This was impossible, even though it would have worked on a generic setup.

Terje

--
- <Terje.Mathisen@xxxxxxxxxxxxx>
"almost all programming can be viewed as an exercise in caching"

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