dr@ski.UUCP (David Robins) (05/18/86)
I have long been "troubled" by the SSC interrupt forwarding. The SSC
manual mentions special switches on pages 8 and 24.
"Switch SW2-6 controls forwarding of interrupts to the Apple II.
Since the Apple II and II+ do not handle interrupts,
set SW2-6 OFF."
No further mention is made of this switch, and no mention is made of its
application on //e's.
This switch appears to be simply in the IRQ line coming into the SSC.
Therefore, does this switch enable/disable interrupts coming IN to the
Apple from the outside, does it control enable/disable IRQ's from the
Apple to be somehow passed to the outside, or is the SSC able to
generate IRQ's of its own.
If none of the above, what is the possible function of this switch,
and how would it be used?
--
====================================================================
David Robins, M.D.
Smith-Kettlewell Institute of Visual Sciences
2232 Webster St; San Francisco CA 94115
415/561-1705
{ihnp4,qantel,dual}!ptsfa!ski!dr
The opinions expressed herein do not reflect the opinion of the Institute!jgpo@ihuxe.UUCP (john opalko) (05/19/86)
> I have long been "troubled" by the SSC interrupt forwarding. The SSC > manual mentions special switches on pages 8 and 24. > > "Switch SW2-6 controls forwarding of interrupts to the Apple II. > Since the Apple II and II+ do not handle interrupts, > set SW2-6 OFF." > > ... > > ... what is the possible function of this switch, > and how would it be used? > The SSC generates an interrupt every time a character comes into the UART. The //e can handle interrupts, even though DOS doesn't. Pro-DOS does, however. Some terminal programs, such as "Ascii Express," handle interupts. If you are running Pro-DOS, and write an appropriate interrupt handler, or if you are running a terminal program that handles interupts, you can turn the switch ON and have a better chance of not missing characters than if the program was forced to poll the SSC for an incoming character. I can't use "Ascii Express" on my //e at 1200 baud or higher with the SSC interrupt switch off. When I turn it on, I can run up to 2400 baud without missing characters. Actually, I can run 4800 baud, but it's marginal. Hope this helps, John Opalko AT&T Bell Labs Naperville, IL ihnp4!ihuxe!jgpo