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

This is a discussion on Sequence of events/signals that occur on PC side on PSD dial-up through atd*99# - PPP ; 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 ...

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

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


    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


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

    In article <1166614040.328883.242350@79g2000cws.googlegroups.c om>,
    Fairy wrote:
    >
    >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/sys...s/portmon.mspx

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

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

    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*###
    12-20-2006 10:52:00.762 - Recv:
    12-20-2006 10:52:00.762 - Interpreted response: Informative
    12-20-2006 10:52:00.762 - Recv:
    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: }#!}"} } }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}'}"}(}
    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,



    Patrick Klos wrote:
    > In article <1166614040.328883.242350@79g2000cws.googlegroups.c om>,
    > Fairy wrote:
    > >
    > >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/sys...s/portmon.mspx
    >
    > Patrick
    > =========== For PPP Protocol Analysis, check out PacketView Pro! ===========
    > Patrick Klos Email: patrick@klos.com
    > Klos Technologies, Inc. Web: http://www.klos.com/
    > ================================================== ==========================



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

    In article <1166681507.331197.284380@73g2000cwn.googlegroups.c om>,
    Fairy wrote:
    >Hi Patrick,
    >
    >Thanks for your reply.


    You're welcome.

    >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*###
    >12-20-2006 10:52:00.762 - Recv:
    >12-20-2006 10:52:00.762 - Interpreted response: Informative
    >12-20-2006 10:52:00.762 - Recv:
    >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)

    >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: }#!}"} } }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}'}"}(}
    >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?


    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.

    >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.

    >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
    probably trying to start a PPP session:

    >12-20-2006 10:52:05.872 - Recv: ~
    >12-20-2006 10:52:05.872 - Recv: }#!}"} } }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}'}"}(}


    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: patrick@klos.com
    Klos Technologies, Inc. Web: http://www.klos.com/
    ================================================== ==========================

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