Date : Mon, 06 Aug 2007 22:21:25 +0100
From : C.J.Thornley@... (Chris Thornley)
Subject: Emulating Econet hardware?
Hi,
You could simulate what you need in a FPGA? Or GAL? If you have appropriate
knowledge.
Shift registers (available very cheaply) could be used to move data to the
parallel domain and effectively latching data out at 1/8 the speed.
You could use one of these modules
http://www.active-robots.com/products/accessories/usb-modules.shtml
http://www.active-robots.com/products/fiveco/ethernet-converters.shtml
An Ethernet to econet device would require some sort of router (not bridge)
software to be written. Perhaps hiding the econet datagram's in IP packets.
These could have class C addresses.
This will probably require some static ram and its own dedicated cpu.
The first thing that need doing is for the econet protocol / datagram's /
command, will need to be documented, in an easy to follow form. You should
not have to dies through about 3 technical manuals and a reverse engineered
bridge to figure out how it works.
Chris
/> Christopher J. Thornley is cjt@...
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-----Original Message-----
From: bbc-micro-bounces+c.j.thornley=coolrose.fsnet.co.uk@...
[mailto:bbc-micro-bounces+c.j.thornley=coolrose.fsnet.co.uk@...
uk] On Behalf Of Johan Heuseveldt
Sent: 06 August 2007 21:21
To: bbc-micro@...
Subject: Re: [BBC-Micro] Emulating Econet hardware?
Hi,
On Mon 06 Aug, Chris Johns wrote:
> 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.
And sometimes (=many times) the interrupt is only there when the FIFO buffer
is filled with /two/ bytes. That's why the TUBE software also has two-bytes
protocols.
Meaning, the interrupt has to be served within 8bits time of network speed,
which can be as difficult as for an FDC.
> 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.
Correct. It was an ISA card. I think nowadays the problem remains with
interrupt latency, although modern speeds could make it a bit better. I
think the problem remains though, as certain processor instructions can take
a long time.
The EcoLink card has its own processor system on board. There were two
versions. One with a Z80 from SJ Research, and one with a 6502 for which I
don't know the manufaturer. SJ Research too?
A year ago, there was one on Ebay. Anyone seen it too?
> 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".
Probably the best, and (still) quite a task as a software project! :-)
Greetings,
Johan
--
Johan Heuseveldt <johan@... >
aka waarland
The best place is a Riscy place
A mouse is an elephant built by the Japanese.
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