Date   : Sun, 29 Mar 2009 23:57:00 +0100
From   : pete@... (Pete Turnbull)
Subject: A few Econet questions

On 29/03/2009 20:41, Michael Firth wrote:

> It is connected to pins 1 and 2 of PL2, which connects through the main 
> machine's
> PCB to the Econet socket (as I assume you already know). Assuming this is 
> the
> header is the same orientation as on the older modules, for which the 
> schematic
> is in the Master reference manual, this would actually be the data pins, 
> which rules
> out the clock generator theory.

If this is what I think it is, it's the collision detect IC, the inputs 
of which are connected to the data+ and data- lines.  Not fitted on some 
variants of the board, because after selling lots of modules with the 
collison detect, some bright spark in Acorn figured out that the 
software took care of it anyway, and the hardware wasn't needed.  Well, 
he was almost right.  So after a while, it got re-instated.  I guess 
that what you see is the place to fit the IC but it just happens not to 
be present on the boards you have, or else there's a surface-mount 
version (it's a common quad comparator chip, an LM319 IIRC) fitted 
instead, and the board is laid out to be capable of using either variant 
of the IC.

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York