Siemens SIMATIC S7-300 Manual page 49

No.
5. Write an SMS message which consists of "?Temp1" and send it to the S7 station.
6. Once the message is received, the receive text is evaluated. If the SMS message has an 'Order'
as content, the assigned Order_No (e.g., no. 7 for '?Temp1') will be output on the parameter of FB
"SMS_Meld" and saved in the flag word (MW12) in OB1.
A feedback message with message text (Message_No: 5) and temperature value (MW16) will be
automatically sent back to the sender of the query.
Limitation
If the modem receives more than one SMS requesting data in a polling cycle, the
PLC application program will only answer, at maximum, one SMS.
To answer more than one SMS after one cycle it is necessary to extend the pro-
gramm with a buffer for received SMS, etc.
Sending and Receiving SMS Messages with MD720-3
V 2.1, ID Number: 25545680
6.2 Receiving an SMS message (scenario 3/scenario 4)
Action
6 Operation of the Application
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