Autah-cs.579
net.lan
utzoo!decvax!duke!harpo!utah-cs!lepreau
Wed Apr 21 20:47:50 1982
Able DH/DM feature and Sytek's System 20 and HPCL

We've found it absolutely necessary to use flow control at 9600 on
Sytek's System 20 Tboxes.  2.19Q was extremely slow, but the "final"
release (no 2.19foo stuff, just 20/100 1700 0000 1A V2 in the status
display) is somewhat faster.  Tmuxes are probably slower (than Tboxes).

The good news for users of the Able DH/DM is that they can do all the
flow control internally to the DH via a strapping option.  (I forget
which one now, but it's all in the manual-- wish I'd read the fine print
earlier!)  It will internally flow control on RI, so all you have to do
is wire the DH's RI to the Tbox's CTS and set EIA flow control.  It
works great. Since Unix does modem control in such a non-std way,
stealing this signal doesn't mess up modem control for the LocalNet
ports either. We had already modified getty to do HPCL on dialup lines,
so all works fine once you set DCD and DTR on.  Matter of fact, the net
seems to run better when flow controlled everywhere.  (Xon/Xoff flow
control loses for several reasons, one of which is emacs.)

Hanging up on close is fine except that all the output doesn't get
flushed before the HUP, in 4.1bsd at least.  From a (fairly quick) look
at the tty driver it looks like it should be flushing, for the new
driver at least.  But it ain't.  So as a kludge we added a delay in
dhclose before the hangup is done.  Will send the code of that and the
getty changes if anyone's interested.

Jay Lepreau, harpo!utah-cs!lepreau, Lepreau@Utah-20

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