Modem Programming
Coding of exchanges
At a Glance
Format of the string
When a connection request is made, a 32-byte character string may be sent on the line by the calling station to initialize the connection.
z z z z z z z
The character string which may be sent on the line is in the following format: the Start of the frame field, of 2 bytes in length, containing the value 16#531B, the Password field, of 8 bytes in length, containing the value of the station z password (8 characters), the Type field, (protocol type) of 1 byte in length, containing 16#00 for Uni-telway z mode or 16#01 for ASCII mode, the UTW field, (Unitelway mode) of 1 byte in length, containing 16#00 for a master or 16#01 for a slave, the Slave address field, with the slave address stated in 1 byte , the Number of slaves
1 byte ,
field, stating the number of slave address scanned in the the the
Reserved field, containing
Checksum field, of
Start of the frame
1 byte in length, which checks the frame,
field, of
15 bytes
2 bytes
, all reserved and equal to 0,
in length, containing the value 16#451B, z z
Note: This coding of this string depends on the following parameters:
Station password of the modem configuration screen,
Mode and Options of the communication function.
The "Checksum" is performed over 1 byte, without taking into consideration the value of the most significant byte.
Note: The password must not exceed 8 characters in length .
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Modem Programming
Processing of the string
The following table lists different processing scenarios:
Calling station (TSX MDM 10) z z if the station is configured by default, the modem transmits no character string on the line: z connection without password ( CALL_MODEM z function with option 4),
Slave Uni-telway protocol with addresses Ad0 = 1 and Ad1 = 2.
in all other scenarios, the station sends the character string.
Station called (TSX MDM 10)
Scenario where password management is not configured z the station waits for 5 seconds. If no character string has been received on the line, it switches to Uni-telway master mode and scans the slave addresses Ad0 = 1 z and Ad1 = 2, otherwise the station tests the Password field equal to
FFFFFFFF in hexadecimal: z if the test is valid, the station tests the Type, Mode z and Number of addresses fields, and switches to the corresponding mode.
If the test is invalid, the line is closed.
Scenario where password management is configured z the station tests the received password: z if the password received does not correspond to any password in the list, the line is closed.
z if the test is valid, the station tests the Type, Mode and Number of addresses fields, and switches to the corresponding mode.
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