Appletalk requires the ability to do sdlc in hardware to do it efficiently,
that is why they have an 8530 in the mac. Since the sun also has this, there
should be no reason why you can't do this.
You should look at Inside Appletalk, available at any bookstore that keeps mac
programmer documentation. The spec is really well documented with all the
timings you need. It also contains clues to the hardware implementation on the
8530. You will also want the Zilog 8530 manual, which has all the registers
you need to hit on the 8530 to get it to talk.
I am not real sure about the sun specifics though. Q's that come to mind are
whether the sun brings out the balanaced signals from the chip to the serial
port and how you will get access to the chip directly. Is this through a
driver, or is running as a setuid root process sufficient? (I am interested in
what this takes to implement...)
From personal experience bringing up Localtalk (the non-generic term for 230Kb
Appletalk networking), watch out for the timings between the frames and
during carrier sense. If these are not implemented to really tight tolerances,
you will not be able to talk to some devices. I remember that the IIsi we had
was especially prone to these problems. What we found was that you had to busy
wait on many of the gaps to get them in tolerance. I think this is what causes
the cursor on macs to jitter when there is a lot of localtalk traffic to the
node.
Brian Topping
Catapult Entertainment, Inc.
by