[Coco] hardware port mapping question

[Mark McDougall]

Roger Taylor wrote:

> What I'd like to do is connect 4 CoCo's to each other via ribbon cables
> between all of the expansion ports.  On each CoCo I'd like a dip switch
> (or maybe just hard-wired) that sets the CoCo # to 0-3 and let each CoCo
> see each of the others 8-bit data port in a block of ports starting from
> some free address.
	(snip)
> Each CoCo would map those addresses and see 8 data lines from the other
> CoCos.  Can this project be put together with just ribbon cable and a
> few soldered-in components for each CoCo board?

The problem here is that you have 4 asynchronous bus masters each trying
to access resources on the other buses. This is a messy problem solved
with multi-drop bus architectures and bus arbiters (such as PCI) and/or
collision-detection schemes (such as Ethernet) and/or Master/Slave
protocols (eg. RS485).

If you were simply interested in snooping each of the buses you _could_
set up a matrix of muxes and latches but with each coco running
independently there's little point because you'd have no way of
synchronising any communications.

Perhaps if you offered a little more info on what you're trying to
achieve someone could offer a workable solution. You should also specify
what sort of data rate you'd require.

Regards,
Mark