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

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Fairy - 20 Dec 2006 12:17 GMT

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,
1) What are the sequence of AT commands that get
executed when we do dial-up for PSD call.

2) What are the signals that flow between DTE(PC) and DCE(modem)
during dial-up.

Please respond if anyone has any idea.

Regards,

Fairy

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Richard G. Harper - 20 Dec 2006 23:00 GMT

Google is your friend. http://www.google.com/

That should help you finish your homework.

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> Hi,
>
[quoted text clipped - 16 lines]
>
> Fairy

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Fairy - 21 Dec 2006 06:12 GMT

Hi,

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,

> Google is your friend. http://www.google.com/
>
[quoted text clipped - 27 lines]
> >
> > Fairy

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Richard G. Harper - 21 Dec 2006 11:03 GMT

Frankly this is not the behaviour I'd expect from a modem that's working
properly. If neither the modem manufacturer nor the manual can describe the
behaviour I'd consider the possibility that the modem is faulty.

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> Hi,
>
[quoted text clipped - 86 lines]
>> >
>> > Fairy

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Fairy - 21 Dec 2006 11:50 GMT

Richard,

Can you please tell me the faults that you see here?

Can oyu elaborate?

Thanks and regards,
Fairy

> Frankly this is not the behaviour I'd expect from a modem that's working
> properly. If neither the modem manufacturer nor the manual can describe the
[quoted text clipped - 97 lines]
> >> >
> >> > Fairy

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Richard G. Harper - 21 Dec 2006 21:56 GMT

The events following the non-detected carrier despite a report of a CARRIER
DETECT indicate some sort of problem. The modem thinks it's connecting but
the computer doesn't think the modem is connecting. That's most likely a
hardware fault, though it could be a result of installing the wrong drivers.

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> Richard,
>
[quoted text clipped - 20 lines]
>> >
>> > Thanks for your reply.

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Strings - 08 Apr 2007 13:57 GMT

> Hi,
>
[quoted text clipped - 16 lines]
>
> Fairy

there are ways to spy on the serial port. i suppose you can apply that
to any com port.

g.

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