Path: utzoo!attcan!uunet!husc6!cmcl2!adm!smoke!gwyn
From: gwyn@smoke.ARPA (Doug Gwyn )
Newsgroups: comp.unix.questions
Subject: Re: VT100 terminfo problem
Message-ID: <8521@smoke.ARPA>
Date: 17 Sep 88 21:18:23 GMT
References: <3340@dunkshot.mips.COM>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 28

In article <3340@dunkshot.mips.COM> dce@mips.COM (David Elliott) writes:
>My question is this:  Do some VT100s not do XON/XOFF handshaking
>properly, or is it more likely that we aren't doing XON/XOFF
>correctly?

VT100s to the best of my knowledge perform DC3/DC1 flow control
correctly, but they have a very small input buffer which is
easy to overrun if the host system is not very responsive.

Most UNIX VT100 users who have flow control problems have failed
to execute "stty ixon -ixany" in their .profile or other means
of setting up terminal parameters when logging in.  Applications
are then expected to maintain this part of the terminal handler
state when changing modes, the same way that the bit rate must
be maintained.  Older UNIX systems made this hard to do since
switching out of fully-cooked mode would also disable flow
control.  Modern ones do have the capability of retaining flow
control when switching modes.

Some applications, notable some versions of EMACS, do not honor
flow control and will disable it, thereby rendering terminals
such as the VT100 unusable with those applications.  (Use of
padding or other timing-based kludges is NOT an acceptable
substitute.)  Complain loudly about such bugs to their vendors.

P.S.  If your VT100s have DEI VT640 RetroGraphics enhancements,
you need to enable DC3/DC1 flow control in both the VT100 part
AND the VT640 part.