12 Dec
2005
12 Dec
'05
7:38 p.m.
Message: 5
Date: Sun, 11 Dec 2005 19:35:51 +0000 (GMT)
From: ard at p850ug1.demon.co.uk (Tony Duell)
Subject: Re: Acorn IEEE488 interface
To: cctalk at classiccmp.org
Message-ID: <m1ElWzC-000IyBC at p850ug1>
Content-Type: text/plain
Indeed it is. I ran the IEEEFS ROMs which are available at the 'The BBC
lives' site through a disassembler and both ROMs have a copyright
message saying '(C) Intelligent Interfaces Ltd and Acorn Ltd'.
Could you scan the article? I'd be very interested in it!
I've also got the schematic for the Acorn
System IEEE488 card somewhere - it
wouldn't surprise me if the BBC unit is based heavily on this (I don't think I
It might be, it might not. The 'Acorn' IEEE-488 interface for the Beeb
doesn't seem to be an Acorn design.
The article to find is in 'Electronics and Wireless World' February 1984,
pages 24-26 ('IEEE488 interface for the BBC Microcomputer'). It imples
the interface was actually designed by a company called 'Intellegent
Interfaces'. Anyway, there is a schematic. It's based round a
9914 chip along with the
75160 and 75162 buffers. There's a 5MHz clock circuit, an address
decoder, a data bus buffer, and the normal circuit to de-glitch the page
select line on the 1MHz bus. That's all. Nothing remotely odd.
Link S1 selects system controller mode, link S2 selects active pull-ups
on the IEEE488 data lines.
I've just finished reverse-engineering the board and
it's indeed a very
straight-forward design.
[snip]
I do. I think I might also have the IEEEFS ROM that
goes with it, but I
can't promise that.
I wonder what version you've got. The 0.2 ROM seems
like a beta version,
with lots of 'unused code' in between the different subroutines, and the
0.5 ROM hasn't got any filesystem support, just support for the OSWORD
calls.
[snip]
Hmm, I see what you mean. The manual looks very
comprehensive with lots of
examples - but I can't see where it justifies why the addressing is done in
this way.
I think it was done so the IEEE interface could be accessed as an
ordinary file system (file handles &F0-&FF were reserved for IEEEFS IIRC).
Cheers,
Eelco
12 Dec
12 Dec
11:43 p.m.
The article to
find is in 'Electronics and Wireless World' February 1984,
pages 24-26 ('IEEE488 interface for the BBC Microcomputer'). It imples
the interface was actually designed by a company called 'Intellegent
Interfaces'.
Indeed it is. I ran the IEEEFS ROMs which are available at the 'The BBC
lives' site through a disassembler and both ROMs have a copyright
message saying '(C) Intelligent Interfaces Ltd and Acorn Ltd'.
Could you scan the article? I'd be very interested in it! I do. I think
I might also have the IEEEFS ROM that goes with it, but I
can't promise that.
I wonder what version you've got. The 0.2 ROM seems
like a beta version,
with lots of 'unused code' in between the different subroutines, and the
0.5 ROM hasn't got any filesystem support, just support for the OSWORD
calls.
[snip]
Yes, but why not do a modified version of the HP method (at least on
older machines). Have a file called 'DATA' that talks to the currently
addressed talker/listener. And send the appropriate commands to the
'COMMAND' file to address devices. I think that would have been a lot
clearer.
-tony
Hmm, I see what you mean. The manual looks very
comprehensive with lots of
examples - but I can't see where it justifies why the addressing is done in
this way.
I think it was done so the IEEE interface could be accessed as an
ordinary file system (file handles &F0-&FF were reserved for IEEEFS IIRC).
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