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From: hamilton@uiucuxc.CSO.UIUC.EDU
Newsgroups: net.micro.amiga
Subject: Re: Mechanics of dropping DTR
Message-ID: <148600166@uiucuxc>
Date: Fri, 17-Oct-86 14:17:00 EDT
Article-I.D.: uiucuxc.148600166
Posted: Fri Oct 17 14:17:00 1986
Date-Received: Tue, 21-Oct-86 20:47:32 EDT
References: <257@hao.UUCP>
Lines: 30
Nf-ID: #R:hao.UUCP:257:uiucuxc:148600166:000:1319
Nf-From: uiucuxc.CSO.UIUC.EDU!hamilton    Oct 17 13:17:00 1986


hull@hao says:
> If you have a
> program that fails to close properly when it quits, then the device count
> is already at least one when VT100 starts up.  Thus when VT100 quits, the
> count remains greater than zero and DTR remains asserted.
> I wonder why I can't blast the count to zero by ... the "hang up" menu
> option in the VT100 program. ... It seems to me that if a program requests
> exclusive use of the port, and the count is already up by one, then the
> AmigaDOS response had ought to be to return an error for the dev Open call.

    v2.1 vt100 didn't have any code to hangup; the menu item was there,
but it didn't do anything.  v2.2 has code to close the device, wait .75s,
then re-open it, so the open count will remain unchanged afterward.
    if the open count is non-zero and vt100 requests exclusive access, the
OpenDevice will fail.  actually the logic is like this:
	if open count == 0
		no problem; you got it
	else
		if current mode is "shared" and new mode is also "shared"
			you got it
		else
			open fails

	wayne hamilton
	U of Il and US Army Corps of Engineers CERL
UUCP:	{ihnp4,pur-ee,convex}!uiucdcs!uiucuxc!hamilton
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CIS:    [73047,544]			PLink: w hamilton