Acorn IEEE488 interface
eelco at huininga.nl
Mon Dec 12 13:38:13 CST 2005
> 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
>>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
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!
> 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
> 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
> 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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