My thoughts exactly, Tony. There are even enough app-notes dealing with this
problem that one should be able to find one for nearly any single-chipper. The
trick is to find the details on the old MM5740 to enable one to emulate it in a
single-chipper that can subsequently be patched into the application circuit.
Given an i875x or even i8748, that shouldn't be too hard. It's really a
preference issue once one gets to that point.
Dick
----- Original Message -----
From: "Tony Duell" <ard_at_p850ug1.demon.co.uk>
To: <classiccmp_at_classiccmp.org>
Sent: Tuesday, August 21, 2001 12:10 PM
Subject: Re: Apple II+ Keyboard Encoder
> > something I can't see because it's not out of the box (yet). If the MM5740
> > (I'll look it up later, in an old NSC MOS LSI databook) is just a ROM lookup
> > table, an exacto knife and a few wires will allow it to be adapted to a 2732
or
>
> It's not. It includes a ROM table, but it's a complete keyboard encoder
> chip, with the scan counters, etc in it. You could hack a single-chip
> micro in place of it, but not just a 2732 or simialr.
>
> Programming a 8751 or similar (or whatever your favourite microntroller
> with enough I/O (you might want to use external binary to 1-of-n
> decoders) is) to replace a keyboard encoder chip is a reasonable first
> embedded microcontroller project, actually. It's not a time-critical
> application, so your code doesn't have to be efficient.
>
> -tony
>
>
Received on Tue Aug 21 2001 - 14:27:19 BST