Sequence of events/signals that occur on PC side on PSD dial-up through atd*99#

Discussion:

(too old to reply)

Fairy

2006-12-20 11:27:20 UTC

Hi,

When I try to make a PSD call through dial-up using AT command atd*99#,

what are the sequence of events that occur on PC side.

I am making dial-up on UART using RS-232 cable.

To be more specific, what are the sequence of AT commands that get
executed when we do dial-up for PSD call.
Also what are the signals that flow between DTE(PC) and DCE(modem)
during dial-up.

Please respond if anyone has any idea.

Regards,
Fairy

Reply »

Patrick Klos

2006-12-20 18:46:30 UTC

Permalink

Post by Fairy
Hi,
When I try to make a PSD call through dial-up using AT command atd*99#,
what are the sequence of events that occur on PC side.
I am making dial-up on UART using RS-232 cable.
To be more specific, what are the sequence of AT commands that get
executed when we do dial-up for PSD call.
Also what are the signals that flow between DTE(PC) and DCE(modem)
during dial-up.

Try PORTMON to dump the data going back and forth over your serial
connection. I think you can see some of the modem signal interactions
as well:

http://www.microsoft.com/technet/sysinternals/utilities/portmon.mspx

Patrick
=========== For PPP Protocol Analysis, check out PacketView Pro! ===========
Patrick Klos Email: ***@klos.com
Klos Technologies, Inc. Web: http://www.klos.com/
============================================================================

Fairy

2006-12-21 06:11:47 UTC

Permalink

Hi Patrick,

Thanks for your reply.

I took the modem logs while making a data call through dial-up. I saw
the following sequence:

12-20-2006 10:51:56.356 - Send: ATDT*###<cr>
12-20-2006 10:52:00.762 - Recv: <cr>
12-20-2006 10:52:00.762 - Interpreted response: Informative
12-20-2006 10:52:00.762 - Recv: <lf>
12-20-2006 10:52:00.762 - Interpreted response: Informative
12-20-2006 10:52:00.762 - Recv: CONNECT
12-20-2006 10:52:00.762 - Interpreted response: Connect
12-20-2006 10:52:00.762 - Receive Connect but CD was low, Waiting for
signal to go high
12-20-2006 10:52:00.793 - After waiting 20ms CD is still low.
12-20-2006 10:52:00.825 - After waiting 20ms CD is still low.
12-20-2006 10:52:00.856 - After waiting 20ms CD is still low.
12-20-2006 10:52:00.887 - After waiting 20ms CD is still low.
12-20-2006 10:52:05.794 - CD never went high, Proceeding with
connection.
12-20-2006 10:52:05.794 - Connection established at 9600bps.
12-20-2006 10:52:05.794 - Error-control off or unknown.
12-20-2006 10:52:05.794 - Data compression off or unknown.
12-20-2006 10:52:05.872 - CD dropped--Remote modem hung up.
ModemStatus=00000010
12-20-2006 10:52:05.872 - While processing CD dropping, CTS or DSR was
found low.
12-20-2006 10:52:05.872 - Hanging up the modem.
12-20-2006 10:52:05.872 - Recv: ~
12-20-2006 10:52:05.872 - Unknown Response
12-20-2006 10:52:05.872 - Recv: <ff>}#<c0>!}"} } }4
12-20-2006 10:52:05.872 - Unknown Response
12-20-2006 10:52:05.887 - Recv: }
12-20-2006 10:52:05.887 - Unknown Response
12-20-2006 10:52:05.887 - Recv: "}&} } } } }%
12-20-2006 10:52:05.887 - Unknown Response
12-20-2006 10:52:05.903 - Recv: }
12-20-2006 10:52:05.903 - Unknown Response
12-20-2006 10:52:05.903 - Recv: &}*<8b>9<cd>}'}"}(}
12-20-2006 10:52:05.903 - Unknown Response
12-20-2006 10:52:05.919 - Recv: "

I have 2 questions here:

1) CD is asserted high by DCE when connection has been established with

remote equipment. So I should receive CONNECT after CD goes high. How
do I receive CONNECT even thought the CD was low?

2) At a point logs say : CD never went high, Proceeding with
connection.Connection established at 9600bps.
Here the question is If connection was not established with remote
equipment, how is DCE proceeding with the connection and how it says
that the connection is established at 9600bps?

Thanks and regards,

Post by Patrick Klos

Try PORTMON to dump the data going back and forth over your serial
connection. I think you can see some of the modem signal interactions
http://www.microsoft.com/technet/sysinternals/utilities/portmon.mspx
Patrick
=========== For PPP Protocol Analysis, check out PacketView Pro! ===========
Klos Technologies, Inc. Web: http://www.klos.com/
============================================================================

Patrick Klos

2006-12-21 18:32:12 UTC

Permalink

Post by Fairy
Hi Patrick,
Thanks for your reply.

You're welcome.

Post by Fairy
I took the modem logs while making a data call through dial-up. I saw
12-20-2006 10:51:56.356 - Send: ATDT*###<cr>
12-20-2006 10:52:00.762 - Recv: <cr>
12-20-2006 10:52:00.762 - Interpreted response: Informative
12-20-2006 10:52:00.762 - Recv: <lf>
12-20-2006 10:52:00.762 - Interpreted response: Informative
12-20-2006 10:52:00.762 - Recv: CONNECT
12-20-2006 10:52:00.762 - Interpreted response: Connect
12-20-2006 10:52:00.762 - Receive Connect but CD was low, Waiting for
signal to go high
12-20-2006 10:52:00.793 - After waiting 20ms CD is still low.
12-20-2006 10:52:00.825 - After waiting 20ms CD is still low.
12-20-2006 10:52:00.856 - After waiting 20ms CD is still low.
12-20-2006 10:52:00.887 - After waiting 20ms CD is still low.

(Wow... 5 seconds is a long time to NOT get CD)

Post by Fairy
12-20-2006 10:52:05.794 - CD never went high, Proceeding with
connection.
12-20-2006 10:52:05.794 - Connection established at 9600bps.
12-20-2006 10:52:05.794 - Error-control off or unknown.
12-20-2006 10:52:05.794 - Data compression off or unknown.
12-20-2006 10:52:05.872 - CD dropped--Remote modem hung up.
ModemStatus=00000010
12-20-2006 10:52:05.872 - While processing CD dropping, CTS or DSR was
found low.
12-20-2006 10:52:05.872 - Hanging up the modem.
12-20-2006 10:52:05.872 - Recv: ~
12-20-2006 10:52:05.872 - Unknown Response
12-20-2006 10:52:05.872 - Recv: <ff>}#<c0>!}"} } }4
12-20-2006 10:52:05.872 - Unknown Response
12-20-2006 10:52:05.887 - Recv: }
12-20-2006 10:52:05.887 - Unknown Response
12-20-2006 10:52:05.887 - Recv: "}&} } } } }%
12-20-2006 10:52:05.887 - Unknown Response
12-20-2006 10:52:05.903 - Recv: }
12-20-2006 10:52:05.903 - Unknown Response
12-20-2006 10:52:05.903 - Recv: &}*<8b>9<cd>}'}"}(}
12-20-2006 10:52:05.903 - Unknown Response
12-20-2006 10:52:05.919 - Recv: "
1) CD is asserted high by DCE when connection has been established with
remote equipment. So I should receive CONNECT after CD goes high. How
do I receive CONNECT even thought the CD was low?

All modems act differently. This modem doesn't look like it ever
asserted CD (according to your log output). Even if it did, I've
seen different modems assert CD at different times of the negotiations;
some at the same time as CONNECT, and some well after the CONNECT message.

Post by Fairy
2) At a point logs say : CD never went high, Proceeding with
connection. Connection established at 9600bps.
Here the question is If connection was not established with remote
equipment, how is DCE proceeding with the connection and how it says
that the connection is established at 9600bps?

Well, the modem did send the CONNECT message, so the connection probably
was established. Maybe your serial cable to the modem doesn't have the
CD line?

It's also odd that the log would say "CD dropped" when it never showed
CD going high.

Post by Fairy
12-20-2006 10:52:05.872 - CD dropped--Remote modem hung up.
ModemStatus=00000010
12-20-2006 10:52:05.872 - While processing CD dropping, CTS or DSR was
found low.
12-20-2006 10:52:05.872 - Hanging up the modem.

And then after that, the modem sent data to the PC that looks like it's

Post by Fairy
12-20-2006 10:52:05.872 - Recv: ~
12-20-2006 10:52:05.872 - Recv: <ff>}#<c0>!}"} } }4
12-20-2006 10:52:05.887 - Recv: }
12-20-2006 10:52:05.887 - Recv: "}&} } } } }%
12-20-2006 10:52:05.903 - Recv: }
12-20-2006 10:52:05.903 - Recv: &}*<8b>9<cd>}'}"}(}

Yup. It was definately trying to talk PPP here.

Does this modem seem to work properly with Hyperterm and a standard dial-
up connection?

Patrick
=========== For PPP Protocol Analysis, check out PacketView Pro! ===========
Patrick Klos Email: ***@klos.com
Klos Technologies, Inc. Web: http://www.klos.com/
============================================================================