SUMMARY: DTR/getty problems after modifying zsadtrlow.

From: Guntram Wolski (seidc!
Date: Thu Aug 15 1991 - 14:41:17 CDT

A while ago I asked what setting the zsadtrlow variable to 5 did in
order to fix "the DTR problem." First off a definition: the DTR
problem was that after a machine running SUNOS 4.1.1 was up for an
indeterminate amount of time with a getty running on a serial line
(ttya in my case) along with uucp running on that line, the DTR signal
would not be asserted after a dial out. Therefore the modem would not
pick up the phone (even though ps showed a getty running). The answer
on how to fix this was to set the zsadtrlow variable to 5:

% adb -w -k /vmunix /dev/mem
zsadtrlow?W 5
zsadtrlow/W 5

Well, I had tried this and again after some indeterminate amount of
time, dial outs were failing! uucp would have log entries along the
lines of "FAILED (generic open)." I didn't get any answers as to what
the cause might be for me (I did receive some good general answers as
what to look for when uucp fails like this), so I tried rebooting!
Wouldn't you know it, everything has been working fine ever since
(knock wood).

As to what zsadtrlow does, it is the integer number of seconds used to
to hold down dtr when dcd drops.

Hope this enlightens someone.
Guntram Wolski
Sequoia Semiconductor, Inc. 408-438-5331 x112

My original question:

 A while ago, Jim Anderson <> sent out a
   response for the DTR problem (getty/SUNOS doesn't raise getty after
   dialing out, so dialins fail):

> First, thanks to everybody for their help on the DTR problem. The
> solution, as most people probably already found out, is to change the
> zsadtrlow variable to 5. The appropriate technique is:
> % adb -w -k /vmunix /dev/mem
> zsadtrlow?W 5
> zsadtrlow/W 5
> $q

   I tried this on my SparcStation 2 running 4.1.1 Rev. B, and once
   applied, dialins would work great (DTR was always at its proper
   state), but both tip and uucp would start failing! tip would always
   let me know that "all ports busy" and uucp would fail with a message
   in the logfile:

   ....stuff deleted.... FAILED (generic open)

   Can someone please enlighten me (i.e. what is zsadtrlow?, what is
   this patch doing?, why can't I find any information on this bug
   in the SUN bug BBS, etc.)

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