Date   : Thu, 04 Aug 2005 21:56:48 +0200 (BST)
From   : Johan Heuseveldt <johan@...>
Subject: Acorn Econet Bridge

Hi all,

Just done some searching in the messages, but couldn't found anything
specificly stated about a schematic for the Econet Bridge (cheese wedge)
beeing available. Nor that someone is working on it.

Status first:

My thanks to Mark Usher as he sent the (EP)ROM image to me of the Acorn
Econet Bridge; and I've been busy since! :-)

I've done some writing to disassemble the ROM image on the Risc PC, using
an existing 8bits BASIC programme. ATM it works, but there's hardly any
WIMP interface present, but the ROM code is disassembled now. It has been
tydied up a little to iron out the most obvious 'errors' from the
disassembler, and leaving out the empty chunks of the ROM.

Then it took me two days to get an old matrix printer ready to put the
disasembly on paper, as that's the way I prefer. I also scanned the data for
the ADLC and made that into a 23 paged document, which is far easier to
handle/cope with than a 2000+ page book. And the text is larger, so that
makes it better to read too.

I did some quick looks on the disassembly, and it was easy to figure out
that the ADLC'c are at addresses &C800 and &D800. But also addresses &C000
and &D000 are used. Could be some memory logic?

The ROM is split in two address areas: &E000 and &F000. I just wonder
if that has something to do with hardware as well, as the difference
is the A12 address line. It's just something I have to keep in mind when
looking onto the code seriously. But for the moment there's absolutely
nothing pointing that way.

As these extra adresses (&C000/&D000) are used a lot, and having no idea
what its purpose is, that's really something I should know before
continueing.

So the question now is: is the schematic available somewhere?
If not, is someone already working on it?
If not, I can start on that, but would like to make sure no one else is
doing that already.
(I found my Bridge while searching/finding sevaral matrix printers)


greetings,
Johan

-- 
Johan Heuseveldt <johan@...              >
  aka  waarland

  The best place is a Riscy place
 
Brevity is the soul of wit. - William Shakespeare