Date   : Sun, 29 Mar 2009 20:41:19 +0100
From   : mfirth@... (Michael Firth)
Subject: A few Econet questions

----- Original Message ----- 
From: "Phil Blundell" <philb@...>
To: "Michael Firth" <mfirth@...>
Cc: <bbc-micro@...>
Sent: Sunday, March 29, 2009 7:30 PM
Subject: Re: [BBC-Micro] A few Econet questions


> On Sun, 2009-03-29 at 18:24 +0100, Michael Firth wrote:
>> Does anyone here know anything more about the unpopulated IC4 on the
>> newest of the Acorn Econet modules?
>>
>> [...]
>>
>> There is a suggestion that it is for allowing the interface to provide
>> a clock to the Econet, and the connections from the unpopulated IC
>> directly to two pins of the header that connects to the Econet
>> connector seems to also point to this.
>
>>From the photos at the links you mentioned, I would guess that IC14 is
> intended as an alternative to IC7, perhaps as a design backup in case
> the surface-mount part was unobtainable for some reason.  It's hard to
> tell from the photos alone though and I don't have one of those boards
> to look at.

I might be able to help you out if you wanted one, as I'm going to be 
eBaying
6 in the near future due to an over-supply...
>
> Which pins on the Econet header is this IC actually connected to?  Can
> you see where any of the other tracks go to?
>
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.

Interestingly, on closer examination, it looks like these tracks go past as 
well as to
this IC - the connections to the Econet socket go to pins 14 and 15 on the 
IC, but
these pins are then directly connected on the other side of the board to two 
of the
four links to the left of IC4.

It then looks like these links are connected to IC7, suggesting that the 
links connect
IC7 into IC4 and the Econet socket.

Pin 1 on the IC4 goes to the +5V plane, and pins 4-7 go to the ground plane. 
Pins
2 and 3 are connected to the other two links, and also elsewhere on the 
board.
Pins 8-13 and 16 seem to be N/C.

Perhaps this was for some sort of filter IC?

Still not sure what installing the links would enable though...

Regards

Michael