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Re: Apple II VGA Video Generator Card Project
Mark McDougall wrote:
Alex Freed wrote:
But that will require a "flying cable" from the card to the keyboard
connector, and a switch matrix emulation for machines prior to the
IIgs and an ADB emulation for the IIgs.
I don't agree. Apple 2 uses an ascii code from a keyboard. A 7 bit
code with the MSB indicating that a byte is ready. No switch matrix to
emulate. That is a pain in the butt as I know from a ZX Spectrum in an
FPGA project.
Exactly. And even if that wasn't the case, it would be simple to create
FPGA images for each 'flavour' and then program the device with
whichever the user requires.
As for the 'flying lead' - not needed - I'd suggest disabling/removing
the AY3600 entirely and have the card respond to accesses at the
appropriate memory locations.
It's a little harder than that. The encoder is multiplexed with
other main board inputs before getting to the data bus.
Either you have flying leads or you put most of the Apple II on
the card, including pushbutton inputs, etc. (BTW, you have to
supply the pushbutton inputs anyway to get Open-Apple, Closed-
Apple, and the Shift key mod.)
However I don't think USB interface for a keyboard is called for. Most
keyboards in non-Mac world use a PS/2 interface that is infinitely
easier to support.
People have asked for it. Yes, PS2 is easier, but you'll find PS2
keyboards are starting to slowly disappear.... bought a Dell lately?
Everything is slowly disappearing...including us. ;-)
-michael
Parallel computing for 8-bit Apple II's!
Home page: http://members.aol.com/MJMahon/
"The wastebasket is our most important design
tool--and it is seriously underused."