Re: cross point switch

From: Andre Fachat (
Date: 2004-05-20 18:38:07

Hi Jim,

what do you mean by 8x8 crossboard switch?

I have emulated the C64 keyboard with my CS/A65 system, so I have
the schematics for a keyboard emulator at
It uses a 256 byte RAM array that the emulating CPU
writes to and the C64 reads from, using the CIA output
as addresses. So it's similar to the EPROM version,
but I can use shift/ctrl etc keys as well.
But probably this is more hardware than you wanted...

However, If you use not a 64k EPROM (8 bit input from 
CIA and 8 bit char code), but, say a 256k EPROM you can
emulate control keys as well: 8 bit input from CIA, 
8 bit char/key code, 1 bit=shift, 1 bit=ctrl
-> 18bit input -> 256k
If you use a 1M EPROM, you could even use left/right shift,
ctrl and C= keys :-) and any combination thereof.
It can still not handle two other keys pressed simultaniously.
(The RAM solution I used above can)

I guess it's just a matter of your requirements.


On Thu, May 20, 2004 at 01:26:29AM -0500, Jim Brain wrote:
> >
> >I am trying to build a keyboard eliminator that does not require a cross 
> >point switch to "emulate" the 64/128 keyboard.  However, in the event my 
> >idea does not pan out, anyone know a part number for a 8x8 or so switch 
> >that is not as big as the 40 pin monster on 64-KEYB?
> >
> >I'd like a plan B so my idea doesn't evaporate....
> >
> >Jim

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