Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!cbosgd!ihnp4!ihuxe!jgpo
From: jgpo@ihuxe.UUCP (john opalko)
Newsgroups: net.micro.apple
Subject: Re: Apple Super Serial Card "interrupts"
Message-ID: <1301@ihuxe.UUCP>
Date: Mon, 19-May-86 11:04:59 EDT
Article-I.D.: ihuxe.1301
Posted: Mon May 19 11:04:59 1986
Date-Received: Fri, 23-May-86 05:22:01 EDT
References: <250@ski.UUCP>
Distribution: net
Organization: AT&T Bell Laboratories
Lines: 33

> 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