SUMMARY: Telebit TTY adb patch

From: E. Mike Durbin (
Date: Fri Jun 11 1993 - 06:05:06 CDT

My origional Post:
> I remember a patch for the tty driver for Telebit modems. Something
> about the time the telebit takes to reset and go back to command mode.
> The patch was an adb script that increased a timeout amount.
> Anyone know about this? Could anyone send me the patch (adb script).
> Thanks!!
> P.S. The problem is that the getty "sometimes" doesn't cause DTR to be
> asserted, so the modem doesn't answer. Killing the getty fixes the problem
> (DTR comes back).

I received the ADB script I was looking for, but it hasn't completely fixed
my problem. For those that need it:

           1) patching the kernel on the fly:
              # adb -w -k /vmunix /dev/mem
               zsadtrlow/W 6
               zsadtrlow?W 6

        - or -

           2) patching object files and make a new kernel
              # cd /usr/sys/`arch`/OBJ
              # adb -w zs_async.o
              zsadtrlow?W 6

I also got a nice description of the problem forwarded by Guntram Wolski.

My problem turns out to be different, plus my modem is attached to a ports
card, not the on-board serial ports.

My problem shows up as the getty running, blocked in open as it should, but
no lights (DTR, etc) asserted on the modem. The port is not hung, I can
kill the getty, and the new getty succeeds in asserting DTR.

Guntram Wolski suggested putting a timeouit in the gettytab entry (to#60).
This doesn't work. The getty doesn't time out if it is blocked in open (or
at least, it doesn't appear to).

Michael Harris suggested putting a wrapper around getty that sleeps before
starting the 'real' getty, preventing any race condition. As the above
remedies haven't worked, I'll be trying this one next!

Thanks everyone!!gwolsk (Guntram Wolski)!mike (Michael Sullivan)!david (David Beckemeyer)
    Athena.MIT.EDU!raoul!mharris (Michael Harris)

E. Mike Durbin 3rd Party Hardware & Software
Open Business Systems, Inc. Software Development
Authorized Sun VAR System & Network Integration 708-250-0260 1-800-352-8956

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