You may not need to get down to the hardware level. You may be better off
basing your software on an existing model, such as the Open Data-Link
Interface (ODI) specification. This way, you wouldn't have to adjust for
each type of network card, but could work with a single model. Also,
you'll save much development time by using ODI-compliant drivers
already in use for many network cards. Your software could then coexist
with other software that uses ODI protocol stacks--AppleShare PC,
for example.
Since an ODI-based driver already exists for the LocalTalk PC Card, you
could concentrate on developing your server software and basing it on the
available AppleTalk protocol stack. If you want to implement a different
protocol stack for the LocalTalk PC card, this also can be done within the
framework of ODI, and it would still take advantage of the existing driver.
The best source of information on programming to the ODI specification is
the Open Data-Link Interface Developer's Guide, available from APDA. Here
is the introduction to Chapter 1:
"The Open Data-Link Interface is a new system jointly developed by Apple
Computer, Inc., and Novell, Inc., that provides unmatched flexibility for
both network developers and end users. The Open Data-Link Interface (ODI)
includes the Multiple Link Interface (MLI) and the Multiple Protocol
Interface (MPI). The MLI and MPI are the interfaces for network card
drivers and protocol stacks to the Link Support Layer (LSL). The LSL
provides packet transfer between these interfaces in a way that allows
different protocol stacks to use link-level drivers interchangeably and
simultaneously. The ODI puts an end to the need for one-driver to
one-stack communication."
The entire publication includes the Developer's Guide, some sample driver
notes, and a disk with code and test programs. It is available from APDA
as part number M0355LL/A.
For more information, search on "APDA"