DMZ32 and MDMBUF

[David Brown]

Has anyone had any luck with the MDMBUF ioctl (stop/start output when
carrier drops) in 4.2BSD or ULTRIX?

I've heard that the support for MDMBUF is implemented in drivers for
some hardware, but not others (e.g. dh, dz...).  Is that true?  If so,
does anyone know if it is supported by the dmz32 driver in ULTRIX 1.1?

If (as I fear) the answer is not supported, does anyone have any other
suggestions?  I'm trying to hook up some serial printers that use DTR
for flow control to our 11/750 running ULTRIX 1.1 with a DMZ32
multiplexor (this is DEC's new 24-line MUX with remote panel).  This
particular machine does not have a source license (though all of our
others do).  The printers only drop DTR on buffer full; they do not
send XOFF.

In the past, I've hooked up serial printers in a variety of ways:

1) on our pdp11, which is a v7/2.8 hybrid, I added some modifications
to the tty and dh drivers which were on the 1980 Usenix tape (tektronix).

2) on our VAX 11/780, I used some jumpers on the Able DH/DM board
that select hardware flow control (via pin 22 - RING) on individual lines.
This was my favorite solution, as it required no software change (just
a special cable).

3) I could purchase a printer buffer box that uses XON/XOFF for flow
control.

Thanks in advance
-- 
	David Brown	 (415) 945-2199
	Varian Instruments 2700 Mitchell Dr.  Walnut Creek, Ca. 94598
	{zehntel,dual,amd,fortune,rtech}!varian!david