Porting the TFE (Re: IIgs and OS X filesharing solutions)

[lee@lcremeans.homeip.net (Lee Cremeans)]

mjmahon@aol.com (Michael J. Mahon) wrote in message news:<20040224135522.24987.00000302@mb-m26.aol.com>...

> Ironically, we are now in this very situation, with a third-party
> Ethernet card for the Apple II line, with limited IIgs software
> support and no //e software support.  This may be why Apple
> decided to drop their card.

I have to wonder...the C=64 community has not one, but two working
Ethernet adapters (TFE and RR-Net), while Apple II has one that kinda
sorta works (but only really on the IIgs, and only with TCP/IP), is a
closed design and costs 10x as much as a PC 10/100 card (as well as
one that got to the late design stage, but was never completed). Now
that it's 2004 and you can get Ethernet parts for cheap, I'd like to
try. I don't think I could get the cost per board down to $15, but
considering how simple the design I'm pondering is, it could easily be
cheaper than the LANceGS.

I went over to TFE's website (http://wwww.dunkels.com/adam/tfe), and
looked at the schematics. The overall design of the thing is even
simpler than the CFFA card; it's just a (third-party) board with the
Cirrus CS8900, 20 MHz crystal and Ethernet isolation transformer on
it, plus an address decoder (all of 1 74LS139!) on the cartridge PCB.
It'd be easy enough to port to the II; just change the wiring so that
it decodes to slot DEVSEL space instead of C=64 cart space (very
simple). The CS8900 register window is 16 bytes long, so if my
understanding of II DEVSEL space is correct, it should fit perfectly.
It'd also be easy enough to program (since Contiki comes with working
driver code for it), and since the CS8900 has full documentation
available from Cirrus, modifying or improving the drivers would not be
a problem.

The one thing that bugs me is the US$70/qty 1 cost of the required
CS8900 module. I'm wondering if it'd be cheaper to move the contents
of the module onto the board, then put a 8-pin header on the end for a
dongle (similar to what LANceGS does). Maybe if enough people want it,
I could also include the header for the Embedded Ethernet module.
Also, I'm wondering if we would need a working interval timer to use
this board...I'm doubting it, since even on the C=64 it's not
interrupt-driven, but it's something to look out for.

Going from this, I should have a first draft of the II port in a
couple of days, once I get PCB123 figured out (it's a bit funky at the
moment). I'll post here again with a location once I have something.

Comments, questions, please address them to me here. 

-lee