modems on RT (AIX 2.2.1)
Robin D. Wilson/1000000
robin at sabre.austin.ibm.com
Thu Oct 25 03:16:59 AEST 1990
In article <598 at vta.UUCP> tom at vta.UUCP (Tom Wiencko) writes:
>In article <WINDLEY.90Oct11083039 at cheetah.cheetah.cs.uidaho.edu> windley at cheetah.cs.uidaho.edu (Phil Windley/20000000) writes:
>>
>>
>>I'm trying to get an internal modem to work as a dial-in on an RT running
>>AIX 2.2.1. The problem is that I can't find out how to send an
>>initialization string to it to get it to go into auto answer mode. I've
>
>Send the following commands to your Hayes compatible modem:
>
> E0
> Q1
> C1
> D3
>
Actually the E0 is not required, but setting the port to pdelay or pshare is.. Setting Q1 is also not required, but setting Q1 OR Q2 is.
1) E0 turns off command echo. This means that when you type in
commands on the modem, it will not respond. This is to prevent
the modem from echoing back the login herald when the port sends
it out. Fortunately, if you use pshare, a login herald will not
be issued until CD (carrier detect - rs232 pin 8) is raised by the
modem. Or, if you use "pdelay" the login herald will not be issued
until the modem sends a character to the serial input on the RT.
2) Q1 turns off command response from the modem. This will work
but it will cause problems if you need to use the modem for UUCP
CU, or certain other facilities. This is because these facilities
(by default -- the configuration can be changed to work) use
the command response to detect call progress. (Ie. send the command
"AT", expect "OK" from the modem, dial the number, expect "CONNECT"
from the modem, etc.) Setting the modem to Q2 will cause the modem
to only send responses to command issued from the RT side of the
connection -- not the incoming telephone line side. This will
prevent the modem from saying "RING" or "CONNECTED" when the remote
system dials in. The reason you don't want these responses is because
they will be stored on the serial input buffer as an attempt to login,
causing the first login to always fail... Not a good thing to
happen for reliable serial communications.
The C1 should read "&C1". From my recollection (and from this hayes book
right here in front of me) there is no "C" software switch on the hayes
modems. The "&C1" should set the modem to follow true carrier. This is
very important if the tty is set to "pshare" since; when in pshare mode,
getty will not issue a login herald until it sees carrier come up from the
modem. If the modem is not set to "&C1" the modem will always hold carrier
high, causing getty to alwys issue a login herald (which defeats the purpose
of pshare).
The D3 should read "&D3". The "D" software switch on the hayes modem is to
alert the modem to "Dial". The "&D" switch is to tell the modem how to
handle DTR signals from the DTE device (the RT). The "&D3" tells the modem
to hangup, and reset to stored operating parameters when DTR from the
DTE device is dropped. NOTE: this will dump any settings made to the modem
that you may have made without actually saving them to the default profile.
Another method to accomplish similar results is to set "&D2" instead. This
will tell the modem to "hang up and return to command mode" when DTR is
dropped by the DTE device. This method will not reset the modem. The
reason this setting is significant, is that it will determine the modem's
ability to hangup when the call is terminated by the RT. The RT line
discipline currently will drop DTR for at least 10 milli-seconds after a
logout (or SIGKILL/SIGHUP/etc. on the process running on the tty) is received.
The response of the modem should be to drop carrier, to signal a loss of the
DTE device, and dropping CD should cause the modem to hangup. This is very
important to modem communication because a connection will not hangup if the modem asserts DTR unless the remote site drops carrier. (In other words,
if you logout on the RT, the connection will stay up until you physically
disconnect the line from the remote site.)
Other important settings are:
&K - sets flow control... NOTE: UUCP cannot use XON/XOFF flow
control. This is because UUCP transmits a packet, and then
waits for a response (with a checksum of the received packet).
The checksum value in the response packet can contain the valid
XON/XOFF characters, and willbe stripped out by the modem, or the
serial port drivers if used. However, the RT cannot do RTS/CTS
so you must set "&K0" if you want to use the RT - modem setup
for UUCP.
&K0 -- no flow control
&K4 -- XON/XOFF flow control (can be used for "non-uucp"
connections.)
Anything else won't work (reliably).
S000 - set the number of rings before answering the call. If you
want the modem to autoanswer, set this to a number > 1. Otherwise,
0. Be careful, large numbers will affect the timeout values for
incoming modems (ie. if the number of rings is set to "10" then,
incoming calls will have to wait for 10-11 rings (about 45 seconds)
before the remote modem will answer, add to that several seconds for
negotiating carrier, and there is a good likelyhood that the default
timeout on the remote modem for establishing carrier will be
exceeded, causing the remote modem to say "NO CARRIER" and hang-up.)
The rest can be found in you modem book.
+-----------------------------------------------------------------------------+
|The views expressed herein, are the sole responsibility of the typist at hand|
+-----------------------------------------------------------------------------+
|UUCP: cs.utexas.edu!ibmchs!auschs!sabre.austin.ibm.com!robin |
|USNail: 701 Canyon Bend Dr. |
| Pflugerville, TX 78660 |
| Home: (512)251-6889 Work: (512)823-4526 |
+-----------------------------------------------------------------------------+
More information about the Comp.unix.aix
mailing list