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From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: comp.terminals
Subject: Re: Brain-damaged Terminal Contest
Message-ID: <5398@brl-smoke.ARPA>
Date: Thu, 20-Nov-86 17:07:42 EST
Article-I.D.: brl-smok.5398
Posted: Thu Nov 20 17:07:42 1986
Date-Received: Fri, 21-Nov-86 22:10:59 EST
References: <1438@kitty.UUCP> <1140@mordred.cs.purdue.edu>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 82

In article <1140@mordred.cs.purdue.edu> avr@mordred.cs.purdue.edu (Andrew V. Royappa) writes:
>	Don't know about Most brain-damaged, but the BLIT (dmd 5620, AKA
>Bell Labs Intelligent Terminal (I think) -- it should stand for BLAT --
>Bell Labs Annoying Terminal). I'm on a BLAT right now, and some of it's
>"features" are:
>
>	1. No known termcap escape for reverse vide -- if someone knows it,
>	   please give it to me
>	2. Bad mangling of ^S/^Q with emacs (gosling's, anyway).
>	3. Most infuriating feature -- if too much text is being printed,
>	it just hangs and beeps forever. Makes it tough to page through
>	large files. I usually feel like putting my fist through the
>	screen when this happens.

This terminal is an AT&T/Teletype 5620 Dot-Mapped Display (DMD) terminal,
not a Blit.  The Blit was in effect the DMD's prototype but is not
interchangeable with it.  "Blit" is NOT an acronym.

The real problem here is operator stupidity.  He has disabled flow control
and is complaining about the consequences.  On recent models (firmware
revision 2.0 or later), one can disable DC3/DC1 (^S/^Q, XOFF/XON) flow
control safely, but ONLY within a layer, not in standalone mode.  This
is explained in the operator's manual.  (One thing that isn't explained
is that, on older models, it was important to follow RS-232-C specs in
hooking up the terminal.  It was because of this that for a while I had
the only DMD at BRL that flow-controlled properly.)  You should also note
that the DMD is really intended for operation in layers mode, with
standalone use limited pretty much to just getting logged in before
starting up layers operation.

Use of ^S/^Q as keyboard commands in EMACS was ALWAYS a mistake.  Too
many terminals, particularly fancy models, really do require that these
characters be reserved for hardware flow control for correct operation,
particularly at high baud rates.  (The DEC VT-100 was probably the first
terminal in widespread use for which this was important.)  One should
have bound the search and quote commands to other keys than ^S/^Q, for
use with all terminals, rather than develop such a bad habit.  There are
undoubtedly implementations of EMACS and other programs that don't honor
flow control even when one has instructed the OS terminal handler to
support it ("stty ixon -ixany" on UNIX), but that's a bug, not a feature.

Here are our 5620 termcap entries; recent DMDs support reverse video
and underlining directly in their resident terminal emulator firmware,
although a downloaded terminal emulator could have whatever features it
wanted:

# NOTE: Move tty5620-1 behind tty5620-2 after all DMDs are upgraded!
#
# Teletype 5620, firmware version 1.1 (8;7;3) or earlier
# The following SET-UP modes are assumed for normal operation:
#	CR_DEF=CR	NL_DEF=INDEX	DUPLEX=FULL
# Other SET-UP modes may be set for operator convenience or communication
# requirements.
# This termcap description is for the Resident Terminal Mode.
# Hardware tabs are assumed to be set every 8 columns (default).
# No delays are specified; use "stty ixon -ixany" to enable DC3/DC1 flow control!
TB|tty5620-1|tty5620|dmd|Teletype 5620 with old ROMs:\
	:AL=\E[%dL:al=\E[L:am:bl=^G:cd=\E[J:ce=\E[K:cm=\E[%i%d;%dH:\
	:co#88:cr=^M:DC=\E[%dP:dc=\E[P:DL=\E[%dM:dl=\E[M:do=^J:ho=\E[H:\
	:IC=\E[%d@:ic=\E[@:it#8:kb=^H:kC=\E[2J:kd=\E[B:kH=\E[70;1H:kh=\E[H:\
	:kl=\E[D:kr=\E[C:ku=\E[A:le=^H:li#70:ll=\E[70;H:nd=\E[C:rc=\E8:rs=\Ec:\
	:sc=\E7:SF=\E[%dS:sf=^J:SR=\E[%dT:sr=\E[T:ta=^I:up=\E[A:vt#3:xo:\
	:cl=\E[H\E[J:\
	:bs:pt:
#
# Teletype 5620, firmware version 2.0 (8;7;5) or later
# The following SET-UP modes are assumed for normal operation:
#	DUPLEX=FULL	GEN_FLOW=ON	NEWLINE=INDEX	RETURN=CR
# Other SET-UP modes may be set for operator convenience or communication
# requirements.
# This termcap description is for the Resident Terminal Mode.
# Hardware tabs are assumed to be set every 8 columns (default).
# No delays are specified; use "stty ixon -ixany" to enable DC3/DC1 flow control!
TA|tty5620-2|tty5620|dmd|Teletype 5620 with new ROMs:\
	:AL=\E[%dL:al=\E[L:am:bl=^G:cd=\E[J:ce=\E[K:cm=\E[%i%d;%dH:\
	:co#88:cr=^M:DC=\E[%dP:dc=\E[P:DL=\E[%dM:dl=\E[M:do=^J:ho=\E[H:\
	:IC=\E[%d@:ic=\E[@:it#8:kb=^H:kC=\E[2J:kd=\E[B:kH=\E[70;1H:kh=\E[H:\
	:kl=\E[D:kr=\E[C:ku=\E[A:le=^H:li#70:ll=\E[70H:me=\E[0m:mr=\E[7m:\
	:ms:nd=\E[C:rc=\E8:rs=\Ec:sc=\E7:se=\E[0m:SF=\E[%dS:sf=^J:so=\E[7m:\
	:SR=\E[%dT:sr=\E[T:ta=^I:ue=\E[0m:us=\E[4m:up=\E[A:vt#3:xo:\
	:cl=\E[H\E[J:\
	:bs:pt: