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From: jr@amanue.UUCP (Jim Rosenberg)
Newsgroups: comp.sys.att
Subject: How do you get the 3B1 serial port to respond to BREAK?
Message-ID: <232@amanue.UUCP>
Date: Wed, 19-Aug-87 22:40:13 EDT
Article-I.D.: amanue.232
Posted: Wed Aug 19 22:40:13 1987
Date-Received: Sat, 22-Aug-87 09:27:59 EDT
Organization: Amanuensis Inc., Grindstone, PA
Lines: 43

OK, I give up.  How do you get a getty on /dev/tty000 to change the baud rate
in response to a BREAK?  I have a new 3B1 and would like to put an external
2400 baud modem on the serial port.  I have folks dialing me with 1200 baud
modems who don't have 2400, but don't have a separate line for the two baud
rates.  I changed /etc/gettydefs so 1200 goes to 2400 next and vice versa.
Connecting the 3B1 to a PC-type machine and trying to log in with both PRO-YAM
and PC-VT, the 3B1 would not toggle baud rates when sent a break no matter what
I tried.  This was a direct serial cable with 4-5 and 6-8-20 tied together at
each end, 2, 3 reversed.  It works fine as long as I don't try to change
baud rate.

Paul Homchick (cgh!paul) is in exactly the same boat.  I tried uucp'ing to
his system with a 2400 baud modem on the serial port, and she wouldn't change
baud rate from 1200 to 2400.  The same L.sys entry expect-send sequences *do
work* when I uucp to maxepr, which has a 2400 baud modem starting off at 1200
on an *expansion port*.  Paul tells me Kathy Vincent had the exact same problem
and finally just gave up.  (Any news on that Kathy?)

So, halp!  It says right there in black and white on the man page for getty(1)
she's suposed to flip to the next baud rate when receiving a break.  One thing
I've noticed is that even though BRKINT is in the pre-login gettydefs field,
getty -c shows 0 for iflag, and stty shows -brkint.  On my VENIX machine I
don't have BRKINT in gettydefs, and it will change speed with a break, so
maybe this is a red herring.  But if getty is not responding to iflag settings
why did someone put them there in gettydefs?

On many machines, including my VENIX machine, there is a way to tell the driver
to ignore hardware handshake lines, like the dip-switch settings on most
modems.  The 3B1 doesn't seem to have this.  Are you supposed to go completely
through the termio(7) struct to enable and disable modem control?  ATE has a
form somewhere talking about modem control.  Anybody know how ATE does it?
On my VENIX machine I have a script that will disable the getty and tell the
line to ignore the fact that it hasn't got carrier detect.  This lets me
call out under control of shell scripts, then bring back the getty when the
call is done.  I'm not sure how to do this on the 3B1.

Any help *GREATLY* appreciated.  This is one snazzy machine, but I gotta get
these points figured out before moving all my modem traffic over to it.
-- 
 Jim Rosenberg
     CIS: 71515,124                         decvax!idis! \
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