option PORTSELECTOR

[Piet Beertema]

	>I am running a Vax 750 with a single DZ11 attatched to a Micom Port Selector.
	>We want the system to be set up such that when a user logs out the driver
	>drops the line and the user is returned to the Micom.  When we had the lines
	>set as dialups everything would work fine except for once a tty was
	>disconnected it would not respond to a ring, we could connect 8 times and
	>then no more.
	>I noticed an option in vaxif/dz.c of something like PORTSELECTOR.  Are any
	>of you familiar with this or know if it might solve my problem?
Port type 9 (dialup) is slow and is put out of service too frequently; we use
only port type 8 (DTR). It requires two things:
1. By default HUPCL must be set, so upon close DTR to the Micom is dropped;
2. The Micom requires (on both port types) DTR to stay low for a while (very
   short actually, something like 200nsec seems enough, so a small capacitor
   allows you to connect up e.g. lineprinters to the same port type...); all
   you need to do is to keep DTR low in the dzclose() routine: after dropping
   DTR sleep e.g. .5 sec.:
	{
		extern int wakeup();

		(void) dzmctl(dev, DZ_OFF, DMSET);
		/* Hold DTR low for 0.5 seconds */
		timeout(wakeup, (caddr_t) &tp->t_dev, hz/2);
		sleep((caddr_t) &tp->t_dev, PZERO);
	}

-- 
	Piet Beertema, CWI, Amsterdam
	(piet at mcvax.UUCP)