Problem with modem on S2 serial port

[Robin D. Wilson]

In article <300 at bria.AIX> mike at bria.AIX (Mike Stefanik/78125) writes:
>In article <22165 at orstcs.CS.ORST.EDU>, ghe at nucthy.physics.orst.edu (Guangliang He) writes:
>> In article <281 at bria.AIX> mike at bria.AIX (Mike Stefanik/78125) writes:
>> > I having a bit of a problem with an RS/6000 and a modem on the 
(stuff deleted)
>> > The problem is that when I try to dial up the system, I get a
>> > connect, but no login.
>
>When I called AIX support, that was one of the things that they suggested
>that I do; I've tried CTRL-C, DEL, and BREAK and nothing seems to get
>that modem's attention.

There should be no APARs that are related to your problem.  (Assuming I know
what the problem really is.)  There are several APARs relating to serial ports
and SHARE/DELAY not working.  

The reason "^C" or "BREAK" might work is because they will cycle the getty on
the port and cause it to respawn.  ("^C" will kill the getty, BREAK/DEL will 
cause a framing error, forcing getty to respawn.)  When it respawns, it opens
the port cleanly, and you can login.... This doesn't work probably because your
port has been listed as defective by the OS since it was attempting to login
over and over again until the system figured that it was defective and 
disabled it.

The reason this happens is 2 fold: 1) the modem is setup wrong; that is... it
is setup to respond with "RING" everytime someone calls in, and carrier is
likely strapped high on the modem switch settings (either software or hardware
switches).  When you start a getty (PENABLE) on the port, it locks the port
andthen sits there waiting for carrier.  When carrier is detected, getty calls
the "logger" (normally/default == /bin/login) which issues the login herald.
When the modem has carrier strapped high, getty instantly goes to the logger, 
which sends the herald.  The modem assumes that the herald is an attempt to 
issue a command, but it doesn't recognize the command, so it says "ERROR".
The logger thinks "USER ERROR IS ATTEMPTING TO LOGIN" and sends "password:"
to which the modem responds "ERROR", to which getty restarts, and everything 
starts over again.  After several hundred iterations, the port is marked as
defective, and getty is disabled.  2) The port is set to "ENABLE".  I realize
that at this point, SHARE and DELAY are broken, so proper tty setup cannot be
realized; but for future referance (and 3003 update levels): the port will 
assume that a device (aka. terminal) is directly attached, and will not really 
handle all of the modem idiosyncraies very well. 

If you still have a problem with this, give me a call at the number below....

Please don't expect a great deal of "how-to" assistance, but I can give you
the basic run-down on the tty problems.
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