[BBC-Micro] Using a B keyboard on a Master

Johan Heuseveldt johan at waarland.demon.nl
Mon Jul 13 22:51:15 BST 2009

Hi Andy,

Sorry to be a bit late.

On Fri 10 Jul, Rob wrote:
> 2009/7/10 Andy Ford <acorn at acford.co.uk>:

> > I was wondering if there was a quick way of disabling this (if "that" is
> > the solution) ? , I did search the list but was unable to find anything

I did report on this twice in the past.

> > as its difficult to search for small phrases via Google.
> A quick glance at the circuit diagram points at IC16 as the keyboard
> decoder - is it socketed?  If so, pull it out.

That's indeed the experience I had.
I have only one Master with a socketed keyboard encoder. When
this was removed, the model B keyboard was fully functional!

> Otherwise there seems to be no links or jumpers to select it... if
> it's not, snip pin 38, nKBEN (in a way that means you can solder it
> back together again) and see if that helps...

I assume that the software isn't aware of two keyboards possible,
and with two conected there is a hardware clash somehow.

Please note that the keyboard encoder -in discrete logic - is
built onto the PCB of the model B keyboard (so only 17 wires).
The Master keyboard is just a dumb matrix, and its keyboard
encoder is a single custom chip on the Master mobo, therefor
losts more wires!

I think both encoders get adressed simultanously, and the
system can't cope with that? Both generating an interrupt?


Johan Heuseveldt <johan at waarland.demon.nl>
  aka  waarland

  The best place is a Riscy place

Shine on, you crazy diamond!

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