Date   : Fri, 07 Aug 2009 02:07:26 +0200
From   : rick@... (Rick Murray)
Subject: A new Element 14

Alex Taylor wrote:

> The 3000's also got a non-fitted internal pin header marked
> "Alt.Keyboard" - I've always wondered if this was for connecting up a
> 6-pin mini DIN socket for an external keyboard,

I think so. I dimly recall downloading the A3000 service/tech manual 
ages ago specifically so I could answer myself that question as I 
noticed it too... about two minutes after I bought mine and took the lid 
off to see what was inside...

I don't remember the result. Getting old. Well, I'm only 35 but my 
memory I think came from a 1935 model. :-/


Stupid... Got internet now. Hang on...

Okay, design backup.

Pin 1 - Keyboard reset
Pin 2 - n/c
Pin 3 - 0v
Pin 4 - 5v
Pin 5 - KRX (from keyboard)
Pin 6 - KTX (to keyboard)

It is briefly documented in 
http://www.drobe.co.uk/archives/backwater.vetonline.vic.edu.au/pdf/A3000trm.pdf 
on page 20 (that's p18 in Acrobat Reader).


Does anybody know if there was ever a botch to get an A3000 to spit 
colour on the composite, or it is just a sort of averaging of the RGB to 
make a crude luminance?


Best wishes,

Rick.


-- 
Rick Murray, irregular internet access at local library.
BBC B: DNFS, 2 x 5.25" floppies, EPROM prog, Acorn TTX
E01S FileStore, A3000/A5000/RiscPC/various PCs/blahblah...