Appletalk fake-out from serial port...

Appletalk fake-out from serial port...

Post by Paul Darren Warn » Thu, 14 Jul 1994 05:07:05

I wish to send appletalk packets originating from my SUN through
the serial port.  I have a head shell already converted.  Is
there any way to do this, or am I completely out to lunch...

Hmmm...  It's just that I have this peripheral on some device
that requires being hooked up to a MAC's serial port, using
Appletalk.  Having this data transfer originating from the
SUN would make my life much easier...

Any help appreciated...
Drink milk, eat cookies...
Smile, laugh, love...
And for a change, enjoy...


Appletalk fake-out from serial port...

Post by Brian - Toppi » Wed, 20 Jul 1994 08:24:18

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

Brian Topping
Catapult Entertainment, Inc.


1. faking serial ports

I have an application (no source mods possible) that opens a serial port
by way of open("/dev/tty33", ...) for example.  It then dups its standard
I/O to that descriptor.  Is there any way to work around the hardware
so what is in fact being opened is connected to the standard I/O of another
process (one which I will write)?  If the sources were available for the
application, there'd be no problem.  

I thought about putting a pty wrapper around the application, but when it
closes its standard I/O before the dup, I'd lose the links I need.

Any ideas?  SunOS 4.1.x is the primary target, but SYSV would also be nice.


Mike Garzione                           IEX Corporation

                                        Richardson, TX  75080

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