modem

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Getting the attention of the modem. A modem operates in two modes: commands and data mode. To get the attention of the modem the special string of '+++' is sent to the modem. This causes the modem to leave the data transfer and respond to commands. Thus:

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Get the attention of the modem by sending +++ to it.

Debugging the modem

Once you have the attention of the modem, the AT &V command can be used to view the status of the registers in the modem:

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Enter the AT command of AT &V.

 

The S00 register contains the rings to auto-answer. What value is this?
The S01 register contains the rings counter. What value is this?
The S02 register contains the escape character. What value is this?
The S03 register contains the carriage return character. What value is this?
The S06 register contains the wait time for dial tone. What value is this?
The S07 register contains the wait time for carrier. What value is this?
The S08 register contains the pause time for automatic dialing. What value is this?
The S10 register contains the pause time for automatic dialing. What value is this?
The S12 register contains the escape code guard time. What value is this?
The S29 register contains the Flash dial modifier time. What value is this?

 

It is also possible to view individual registers with:

AT S0?.
AT S1?.
AT S2?.
AT S3?.
AT S4?.

and registers are set with the following format:

AT S0=10.
AT S1=7.

Checking product code/ROM details

The I registers contains information on the modem.

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Enter the AT command of AT I0 for product code.
Enter the AT command of AT I1 and for AT I2 for ROM checksum.
Enter the AT command of AT I3 for product revision code.
Enter the AT command of AT I4 for response programmed by OEM.
Enter the AT command of AT I5 for country code.

Setting word or digit result code

The modem will either gives words back as messages (such as OK, NO CARRIER, and so on), or numeric codes.

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Enter the AT command of AT V0 for numeric codes.
Enter the AT command of AT V1 for words.

Setting speaker volume

The AT Ln command is used to set the speaker volume for the modem:

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Enter the AT command of AT L0 for low volume.
Enter the AT command of AT L2 for medium volume.
Enter the AT command of AT L3 for high volume.

Speaker mode

The AT En command is used to set the operation of the speaker:

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Enter the AT command of AT M0 for Speaker off.
Enter the AT command of AT M1 for Speaker off while receiving carrier.
Enter the AT command of AT M2 for Speaker is always on.
Enter the AT command of AT M3 for Speaker on when dialing, then off.

Command echo

The AT En command is used to set whether the AT command is echo'ed back:

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Enter the AT command of AT E0 for no echo.
Enter the AT command of AT E1 for echo.

Tone/pulse dial

The modem uses tone dial with AT T, or pulse dial with AT P.

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Enter the AT command of AT T.
Enter the AT command of AT P.

Go on-line and into answer mode

The modem is told to go into an answer mode with the AT command of AT A.

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Enter the AT command of AT A.

If you are not connected to a telephone line, the modem will wait for a time-out period, and will display the message: NO CARRIER, else it will wait for a call.

 



Making a call

The modem is told to dial a remote modem with the AT command of AT D.

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For example to dial the number of 123456, the AT command of AT D 123456.

The emulator simulates the non-connection of the modem to the phone line (based on a random event). If it displays a message of NO DIALTONE, keep trying the AT D 123456 command. Otherwise you will get a message that says you are connected, such as CONNECT 9600. You will then get messages from the other side of the connection.

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Type messages which will be sent to the other side. The other side should also send messages to you.

 

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Put the modem back into commands mode with a +++.

 

Hang-up a connection

The modem is told to hang-up a connection with AT H.

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Enter the AT command of AT H.

Test modes

The analogue loopback test is defined with AT &T1.

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Enter the AT command of AT &T1. The commands will then be echo'ed back from the modem. To gain control of the modem enter +++.

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