Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!eos!phil
From: phil@eos.UUCP (Phil Stone)
Newsgroups: comp.sys.amiga.tech
Subject: Interrupt Server, Parallel port
Message-ID: <631@eos.UUCP>
Date: 28 Apr 88 16:12:38 GMT
Reply-To: phil@eos.UUCP (Phil Stone)
Followup-To: comp.sys.amiga.tech
Organization: NASA Ames Research Center, Calif.
Lines: 25
Summary: How to find source of IRQ?

I have built a UART interface that connects to the A-1000 parallel
port. (I've gone through this hell so I could have an RS-232 port *and*
a MIDI port running concurrently).  I think I've got everything ready to
go on the software end except dealing with interrupts.

I understand that I will have to add an interrupt server to the chain that
is already attached to the 8520 (called "PORTS", I think).  I have set up
my UART to assert the "FLAG" interrupt on the 8520, but my question is,
how do I check this bit in the interrupt register without clearing the
whole register?  Actually, since somebody higher up in the chain (timer
interrupts, for example) already had to check this register, it must
*already* be cleared (it automatically clears on reading).

Perhaps the PORTS server passes this register along somehow, but if it
does, I have no way of knowing.  As far as I can tell, the system
interrupt servers are undocumented (correct me if I'm wrong - I've got
the original "white" manual set).

Can anybody help?  Thanks in advance, especially if you can get a reply
(email or post, your judgement on generality of interest) to me before
the weekend.

Phil Stone
phil@eos.arc.nasa.gov
phil@eos.UUCP
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