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From: neil@amiga.UUCP (Neil Katin)
Newsgroups: net.micro.amiga
Subject: Re: Q. on signals
Message-ID: <1224@amiga.amiga.UUCP>
Date: Tue, 27-May-86 14:48:43 EDT
Article-I.D.: amiga.1224
Posted: Tue May 27 14:48:43 1986
Date-Received: Thu, 29-May-86 03:35:16 EDT
References: <8605232155.AA01454@pavepaws>
Reply-To: neil@rocky.UUCP (Neil Katin)
Organization: Commodore-Amiga Inc., 983 University Ave #D, Los Gatos CA 95030
Lines: 29

In article <8605232155.AA01454@pavepaws> dillon@PAVEPAWS.BERKELEY.EDU (Matt Dillon) writes:
>
>	If I WaitIO() on a completed request, will it clear the signal bit?
>NOTE: I DID NOT do a Wait(),  just a WaitIO().  Additionaly, will a
>SendIO() clear the signal bit before starting the operation?  
>
>	Will the signal bit be cleared after a DoIO() ?
>
>						Thanks,
>
>						-Matt

The signal bit is NOT guaranteed to be cleared.  As a matter of fact,
one should never depend on signals to tell when IO is done.

WaitIO first checks to see if the IOB_QUICK bit is set.  Then it checks
to see if the request has been replied.  Then, and only then, does
it do a Wait() on the port's signal bit.

A signal bit may represent many IO requests (if they arrived before you
noticed them) or may not be set at all (if you are allowing QUICK io).
In addition, many calls don't clear the signal bit if the call can tell
that operation has already finished.

Signal bits are an indication that you should look further at a port,
not that something has actually happened.

	Neil Katin
	Commodore-Amiga