Acorn Econet

From: Pete Turnbull <>
Date: Thu Oct 9 02:33:43 2003

On Oct 8, 21:24, Tony Duell wrote:

> I see... Since I intend to start out by linking the ACW to a couple
> other machines (one acting as a fileserver), all on the same bench, I
> assume I can get away with just about any cable :-)

Well, I'd not use tinsel cable or damp string (even with salt) but
apart from that...

> Actually, I am not sure the card in the Atom is a real Acorn one.
> the same circuit, and the same layout, but the PCB is not
> It may be a copy..

Possibly. HCCS made some, I think.

> > > The B+ (in the ACW) has PCB positions for the collision-detect
> > comparator
> > > chip, etc, but they're not fitted....
> >
> > It's worth doing.
> OK, I'll add them sometime. It's farily obvious what to do from the
> schematics (I have those). Will the software make use of the
> detect circuitry, or do I need a particular version of the NFS ROM?

No, all the ROMs I know of can handle that.

> I wondered if you could do that... Alas I don't have the official
> schematics for the clock and terminator, so while I can see the empty
> places for termination resistors on the clock PCB, and while I can
make a
> guess as to the values, I don't know if said guess is good. Do you
> to have a parts list or schematic?

I have a schematic around here somewhere. [hunts through directories
on nearby machine] Ah, that one's for the passive (DIN plug) one:

A three-resistor divider chain, 1K0 at the top, 220R in the middle, 1K0
at the bottom, connected to ground (pin 2). Data+ (pin 1) goes to the
to of the 220R, Data- (pin 4) goes to the lower end. A pair of 56R
resistors goes from each of Clock+ (pin 3) and Clock- (pin 5) to the
top of the upper 1K0. A 10 uF electrolytic goes from the junction of
the 2 x 56R and upper 1K0, to ground.

Jules Richardson has my pile of paper schematics, and I think that's
where the other one is :-(

Oh, but of course I have the box itself. Here we are:

C1, C2: 10uF 10V
C3: 10nF ceramic
R1, R2: 56R
R3: 100R
R7: 470R
D1: OA47 (anything with a low Vf, eg a Schottky diode, should do)
IC3: LM7805
LED1: any old red LED (or you might want to change the colour for
the combined clock/terminator unit)
SK1: 5-pin 180deg PCB DIN socket
SK2: power jack

Fit wire links at LK1, LK2, LK3.

Do you needs the component values for the collision-detect circuitry as
well? I've got B and B+ diagrams here, which show them.

> Well, I am a great beleiver in proper termination (resistors are
> my time in tracing bad signals isn't). So, for example, while I might
> a Unibus for testing with only one terminator (if it's just one
> backplane, say), any machine that I use will have a terminator at
> end. And I'll do the same with Econet.

I should hope so too! You'll see a difference if you remove a
terminator from an Econet of any useful size -- used to be a real
problem in scholls, if they used DIN-plug terminators (kids used to
"borrow" them).

Pete						Peter Turnbull
						Network Manager
						University of York
Received on Thu Oct 09 2003 - 02:33:43 BST

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:36:22 BST