Date   : Fri, 18 Jun 2004 12:17:32 +0100
From   : Philip Blundell <pb@...>
Subject: Re: BeebEm under Linux? (or any BBC emulator under

On Fri, 2004-06-18 at 12:00, Jules Richardson wrote:
> On Fri, 2004-06-18 at 10:25, Philip Blundell wrote:
> > On Thu, 2004-06-17 at 23:21, Dr. David Alan Gilbert wrote:
> > > I don't know how hard hacking ECONET on would be - how complex can the
> > > HDLC chip be? I might have the datasheet somewhere.
> > 
> > It's not terribly complicated; the ADLC is indeed fairly basic.
> > I wrote a 68B54 Econet driver for Linux a few years ago, which
> > I guess you could look at to get some ideas.
> 
> Now that's interesting. How did you interface between the host machine
> and the 68B54 chip?

This was on an Archimedes, which accepts the same plugin module as a
Master.  Later Acorn machines (RiscPC/A7000) have a dedicated Econet
board which is broadly software compatible, and I don't imagine it would
be too hard to make one of those work.  I keep meaning to have a go at
that.

The 68B54 just has a standard 6800-style bus - 8 bits of data, about 3
bits of address, read/write and chip select.  The biggest problem you're
likely to encounter when interfacing it to other machines is interrupt
latency.  Acorn machines always used FIQs in order to guarantee timely
service.

> I'm going to need something with a reasonable amount of horsepower to
> control this picture wall project, as it needs to take an image, split
> it, do the colour processing and then farm out to each BBC within the
> wall for display.
> 
> The plan was to use a later Acorn machine of some sort - with the
> associated learning curve for writing some code for it.

Right; seems like a good plan.  Another possible way of addressing this
would be to graft an Ethernet interface onto a BBC, and set it up to
bridge between Econet and Ethernet.  That way you could run your
crunching on almost any hardware.

p.