vt100 bug

utzoo!decvax!ucbvax!dsp.dove at MIT-SPEECH utzoo!decvax!ucbvax!dsp.dove at MIT-SPEECH
Thu Jul 30 21:24:39 AEST 1981


From: web <dsp.dove at MIT-SPEECH@MIT-AI>
After an exasperating month of frustration I finally discovered why my
vt100's would sometimes hang on output even though I was using xon
xoff properly.  It turns out that if you enable auto xon then for any
^S's you type on the terminal there must be at least one ^Q even if
the ^S's were typed to get some editor to search while the terminal is
in raw mode.  If you neglect to type a ^Q, then the next thing you
send to your terminal at high speed, will break it.  (This assumes
that you don't use TIMEOUT delays but rather xon xoff.)  Try typing a
^S to the shell then interrupting.  A subsequent cat of a file will
break the terminal.  It can then be fixed by a ^Q.  One cure is to not
enable xon xoff.  Another is to type ^Q periodically.  What bugs me is
that you can't disable the auto xon on entry to an editor like EMACS!

Any useful suggestions?

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