Michael J. Mahon (mjmahon@aol.com) writes:
Unless we know that interrupts are actually required for Contiki, this
whole thread is just an exercise.
Adam earlier suggested that the interrupt routine is only used to
update a "real time seconds" clock, which is only polled in the idle
loop to determine (presumably) whether something has timed out.
If this is the case (someone with the source should be able to
tell for sure), then a simple timing loop while idling will do the job
with sufficient accuracy for TCP/IP.
No interrupt source would be needed to run Contiki.
If you really want to play with timer interrupts, then the method of
tapping into VBL (available on _all_ Apple II's) and using it to pull
an open-collector gate low on the IRQ line will do the job. You
may want to use a two-input gate so that an annunciator can
enable/disable the VBL interrupt. In any case, no slot card is
required--this is all doable with wires and machined-pin sockets.
-michael
After digging out the Apple Reference Manual, and being daunted because
despite the schematic in two different places it has to be one of
the most difficult to follow, I remembered that Don Lancaster had done
something along these lines in his "Enhancing Your Apple II, Vo 1"
(was there ever a second volume?).