El 27/09/2010 18:21, Petri Pellinen escribió:
DSMCL can over-ride any decoding internal to the QL, on ANY address.
This was really interesting stuff that defnitely was not in the
documents I found so far.
Maybe you want to take a look at a very simple interface I designed this summer,
which is able to give extra 512KB memory to the original QL. It's an example of
how to drive the DTACK and DSMC signals from your device to the QL, as the
"empty" memory space in the QL is actually "filled" with mirrors of the first
256KB memory page, unless you prevent the QL ULA from doing its thing by pulling
up the DSMC line.
Although it's in Spanish, I think the drawings are self-explanatory.
The original design (schematics), intented to be fitted on the CPU slot (only
for testing purposes, though):
http://www.speccy.org/foro/viewtopic.php?f=15&t=2012
Later on that thread, I show the PCB already built, and explain the inner
details of the GAL that controls the memory expansion. This is when I show how
to drive the DTACK and DSMC signals (last schematic on that post):
http://www.speccy.org/foro/viewtopic.php?f=15&t=2012&start=27
The "final" design, built as a "modchip" to be wired directly to the mainboard:
http://www.speccy.org/foro/viewtopic.php?f=15&t=2056
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