How do I install a modem on a Risc-6000 (AIX3.1.3003)?

How do I install a modem on a Risc-6000 (AIX3.1.3003)?

Post by Tim Fredri » Wed, 13 Mar 1991 02:34:12

There was some discussion about problems with modems a while ago but I
missed out getting copies of what was said.  I want to
set up a fairly generic Hayes compatible modem to dial out with on my
IBM Risc-System 6000/530.  On the Pyramid, the same modem uses RS232 pins
2,3,7,8, and 20.  The same configuration on the 6000 doesn't work for us.
Using an RS232 tester, I see the lights on the AIX end for TD, RTS, and DTR.
On the modem side, nothing.

Can someone who has successfully set up a modem tell me what he did as far
as wiring, configuring tty1 in smit, etc.?  We're using the 8-port serial
unit to connect to.  Thanks in advance.  --Tim


How do I install a modem on a Risc-6000 (AIX3.1.3003)?

Post by Robin Wils » Fri, 15 Mar 1991 00:25:48

>set up a fairly generic Hayes compatible modem to dial out with on my
>IBM Risc-System 6000/530.  On the Pyramid, the same modem uses RS232 pins
>2,3,7,8, and 20.  The same configuration on the 6000 doesn't work for us.

For configuring the wiring I can tell you IBMs official stand is that the
only cable they support is the on they provide... However, that cable will
wire the following pins:

        1, 2, 3, 4, 5, 6, 7, 8, 20

And if you must drop one of these, I recommend "1" (in case you are using
an RJ45 telephone wiring set-up).  

On the tty port side of things, just use "SMIT" to set up the port.  If you
want to use it as "dial-in" and "dial-out" you will need to set up the
field "enable LOGIN" as "share" or "delay".  BUT YOU SHOULD NOTE THAT SHARE

The difference between share and delay (et. al.) reads as follows:

                SHARE - Starts a 'getty -u' on the tty.  Getty waits for
                carrier before locking the port, and sending out a login

                DELAY - Starts a 'getty -r' on the tty.  Getty waits for
                a character on the serial input buffer before attempting
                to lock the port, and send out a login herald.

                ENABLE - Starts a 'getty' on the tty.  Getty locks the
                tty immediately, and then waits for carrier to send out
                the login herald.  (This can only be used for 'dial-in'
                or direct terminal connections.)

                DISABLE - No getty is started, can be used for 'dial-out'

As you can see, the RS/6000 places a lot of credance in the state of
of carrier for determining when to lock the tty and send out the login
herald.  This brings us to the modem setup... Most Hayes compatible
(well, maybe not most... god knows there's a million brands of 'em)
come with the same factory defaults as the original hayes modems.  This
means that carrier is set to "always on" by the modem.  This also means
that is you use the factory defaults, the modem will confuse the getty
on the RS/6K.  If carrier is strapped high, both "SHARE" and "ENABLE"
work work functionally the same, lock the port, and send out a login
herald right away.  If the modem is set to "echo commands" this will
cause all kinds of trouble... The getty will echo a herald, the modem
will echo it back, the tty device will have echo turned on (when getty
is started, the tty device is set to "echo") and will echo it back to
the modem, the modem echos, tty echos, ad. infinitum.  Obviously, the
solution is to set carrier to follow true carrier on the modem.  On the
hayes "V-Series" modems this is accomplished by setting software switch
"&C" to "&C1".

The next important data about the modem setup is what to do when the
RS/6K drops DTR.  The RS/6K uses DTR to signal a "hangup" to the modem.
This means that you must set the modem to use DTR in this manner, or
the RS/6K will not be able to cause your modem to disconnect when the
RS/6K needs it to.  On the hayes "V-Series" modems, the software switch
"&D" controls the modem's response to DTR signalling.  I find that either
"&D2" or "&D3" work best.

Finally, you will need to make sure that you modem does not send any
characters to the tty when people are attempting to dial-in, but before
the carrier is up on the modem.  Hayes modems will send a "RING" message
to the tty device when someone in dialing into the modem.  This "RING"
message will confuse the getty on the port, because it will think that
the user "RING" is attempting to login.  You will usually get a failed
login attempt, and possibly one of the "you used all upper case" login
messages.  So you need to be sure to set the quite mode software switch:
on the "V-series" this is software register "Q".  I find a setting of
"Q2" (respond to local commands only) works just fine.

I am sorry about the length of this posting, but so many people have asked
for this information over-and-over again that I thought I would just
post it all again.


1. Need help with raw mode programs (AIX3.1 Risc-6000)

I am having trouble porting programs that want to use the tty in raw mode
usually for the purpose of serial data transfers.  These programs include
macget, macput, xmodem, pcomm, etc.  They use BSD line disciplines, but
something like:

    stty disp bsd ; macget stuff ; stty disp posix

doesn't seem to work for me.  These programs usually set up the terminal
with calls to ioctl such as:

    struct sgttyb ntty;
    ntty.sg_flags = RAW|ANYP;  /* Sets RAW mode, 8-bit i/f, any parity */
    ioctl (ttyfd, TIOCSETP, &ntty);

Can anyone tell me how to convert these programs to use the posix line
disciplines?  Or has anyone ported macget, macput, xmodem, etc., to the
Risc-System 6000 AIX3.1 successfully?  Can I know what you did?

Thanks in advance.  --Tim

Tim Fredrick             National Center for Atmospheric Research
                         Atmospheric Chemistry Division

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