Date   : Mon, 06 Aug 2007 15:00:33 +0100 (BST)
From   : chris@... (Chris Johns)
Subject: Emulating Econet hardware?

On Mon, 6 Aug 2007, Alex Taylor wrote:

> Would it be possible to emulate an Econet server and clock using a
> PC's parallel port, and suitable software and cabling? A little bit
> like my Commodore 64 setup, where I have a laptop and cable emulating
> a 1541 floppy drive. (Before anyone pounces on this, please don't
> start a flamewar about how parallel ports are obsolete, and this
> should be done with FPGAs/USB/FireWire/ExpressCard).

IIRC, the problem with making anything to connect PC to Econet is interupt 
latency. The ADLC only has a few bytes (i think 3 bytes?) of buffer so you 
need to be quick to read and process the data before it's gone for good.

On the BBC this is done with NMIs (and FIQs on the arc), but I don't think 
the PC has anything that can service an interupt in that sort of speed.

The Econlink ISA cards had their own processors to handle the econet side 
of things, but that makes your design a lot more complicated.

If you have a spare beeb i guess you could connect it via the user port to 
the PC's parallel port to act as a big "econet card".
-- 
  Chris Johns <chris@...             >