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From: fredrick@acd.acd.ucar.edu (Tim Fredrick)
Newsgroups: comp.unix.aix
Subject: How to connect a dial-out modem (the answers for AIX3.1.3002)
Keywords: modem serial rs232 dial hayes
Message-ID: <11020@ncar.ucar.edu>
Date: 11 Apr 91 19:32:59 GMT
Sender: news@ncar.ucar.edu
Organization: NCAR/Atmospheric Chemistry Division
Lines: 47


I got a lot of helpful answers to my question on setting up a dial-out modem
under AIX3.1.3002.  Thanks to everybody who replied.  Here is what I did
to get it to work based on these messages.  My examples use /dev/tty4.

   1. Cable has pins 1,2,3,4,5,6,7,8,20 and 22 wired straight through.

   2. Connect cable to modem and run smit with the power to the modem
      turned on.

   3. In SMIT set up the serial port (in our case tty4) with all of the
      defaults.  Disable logins.  Dial-in and Dial-out capability on the
      same modem isn't supported under AIX3.1.3002 or 3003.

   4. tip or kermit (at least the copy we have) won't work because it
      requires carrier detect to be held high -- my understanding is that
      can't happen with the way the hardware is currently defined.

   5. But "cu" works fine.  We put the following entries in our
      /usr/lib/uucp/Devices file:
             Direct tty4 - Any direct
             ACU tty4 - 2400 hayes \D

   6. And we put phone numbers in the /usr/lib/uucp/Systems file like this:
             atmos Any ACU 2400 9,5554321 - -
             beagle Any ACU 2400 9,5554322 - -

   7. Initially the modem must be configured to hangup the modem with
      a DTR signal.  This is done by entering "cu -l /dev/tty4 -b2400"
      and then:
      7a.  "at &f"                   ---- to fetch S registers from EPROM
      7b.  "at &d2&d3&c1             ---- d2 == modem goes on hook at
                                                returns to cmd mode on dtr off
                                          d3 == modem initializes w/dtr off
                                     ---- c1 == hardware carrier detect
      7c.  "at &w"                   ---- Write S registers to NV RAM
      7d.  Switch the modem off and on again.

   8. To use some systems that only connect at even-parity, we just
      use the "-e" flag on "cu".  For example "cu -e atmos".

BTW, replies also said I needed a null modem cable for attaching dumb terminals
that switch pins 2 & 3 and also exchange handshaking signals (DTR, CTS, DSR)
so that the two sides see the carrier signal.  One person said such a cable
is available from IBM.  I have not yet tried to get a dumb terminal to work.

Good Luck.  --Tim