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Re: PS-2 Keyboard for Aplle II ?

David Wilson wrote:

I think the reason I need to unplug the keyboard ROM is so I can get
access to the KBD' signal. This is so that the microcontroller can
buffer keystrokes and output them one at a time as the motherboard CPU
requests them.

It turns out that a card in slot 1 of a IIe can disable the onboard
keyboard by deasserting ENKBD' (Slot 1 pin 35) and then watch for
accesses to $C000 and $C010.


And what is read for accesses to the $C000..$C01F space is a
little more interesting than what is formally documented.

Not only does a reference to $C01x clear the keyboard strobe,
it also reads the Any Key Down level (sign bit) and the ASCII
keycode of the last scanned key.  In fact, the ASCII code changes
a millisecond or so *before* the sign-bit strobe is set at $C00x.

I note that many emulators do not correctly emulate this behavior,
so that they will not run my real-time synthesizer, RT.SYNTH.  ;-)

-michael

Music synthesis for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
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