Date   : Tue, 26 Jul 2005 00:54:03 +0100
From   : jgh@... (Jonathan Graham Harston)
Subject: Re: ARM copros, speech cartridges, real time

Jules Richardson <julesrichardsonuk@...> wrote:
> > That would be interesting. Take this as a firm order for a Master
> > internal version please. As a point of interest, would it use the
> > Acorn Tube ULA or something different for the hardware interface?
> 
> Presumably the hardware side isn't that difficult, in that it's pretty
> much the same for any CPU? (CPU, bus interface, bit of local memory
 
As long as whatever interfacing hardware looks just like a Tube
ULA from the Beeb side, it's irrelavant how it's implemented. I
was really annoyed when I discovered that Torch's Tube interfacing
hardware using a 6522<->Z80PIO link looked completely different
from the BBC end.
 
The BBC just needs to see:
  &FEE1/3/5/7 data registers, one each direction
  &FEE0/2/4/6 flags saying data present in data registers
 
It could just be implemented as 16 bytes of RAM and appropriate
addressing. IRQ and NMI generation on the parasite could be
implemented with interupt-driven polling on a fast enough
parasite.
 
In fact, I've got some well-developed Tube communication code
written that does Tube communication over a serial port! It can
use any single byte-wide comms channel.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
Sheffield Boundary Review at http://mdfs.net/User/JGH/Docs/Politics/ParlReview