Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!eos!phil
From: phil@eos.UUCP (Phil Stone)
Newsgroups: comp.sys.amiga.tech
Subject: Parallel port interrupt server
Message-ID: <637@eos.UUCP>
Date: 29 Apr 88 17:48:09 GMT
Reply-To: phil@eos.UUCP (Phil Stone)
Organization: NASA Ames Research Center, Calif.
Lines: 20


Restatememt of original question:
	I have built a UART interface for the parallel port so as to be
	able to run RS232 *and* MIDI concurrently.  The UART will send
	interrupts on the FLAG input of the 8520 when it needs
	data or has received data.  How do I distinguish a FLAG interrupt
	from all the other interrupts (timers, PC handshaking, etc.) that
	come from the parallel port?

[ I didn't state this very clearly the first time, sorry ]

I know the kernal must have some way of distinguishing between the different
irq sources, unless the *entire* irq server chain is looking at *every* (timer
event, PC, FLAG, etc.) possible source of irq on the 8520.  This doesn't seem
very efficient to me.  So my original question, once I have added an
interrupt server to the PORTS chain, how do I tell if the FLAG bit was the
cause of the interrupt? (The interrupt register cannot be read directly, as
this action automatically clears it).

[ Thanks for trying to wade through my first garbled attempt at expressing
this problem, Matt. ]