Siemens CP 1243-8 IRC Operating Instructions Manual page 127

Communications functions
The MD720 supports the following extra functions:
● Modes
The MD720 is set to one of the following two modes depending on the type of
communication required:
– OPC mode
– Terminal mode
● OPC mode
In OPC mode, there is productive data exchange with the control center using GPRS.
● Terminal mode
In terminal mode, the MD720 uses CSD communication for the following functions:
– Sending and receiving SMS messages
– Diagnostics and maintenance functions
– Transfer of configuration data
● Communication with a control center
In OPC mode, an MD720 connected to an S7 station communicates with a control center
via a TCP connection. For the data transfer, the GSM network is used with the GPRS
service. Either the MSC protocol or the MSCsec protocol is used (see below).
● Sending and receiving SMS messages
The locally connected application (SIMATIC) can transfer data for an SMS message to
the MD720 using AT commands. The MD720 sends the SMS message to a subscriber in
the GSM network (mobile wireless telephone) or when using a gateway, to a remote fax
machine.
SMS messages received by the MD720 can be queried by the local application using AT
commands.
● CSD communication
Service data calls via remote connections in CSD format are used for the following
purposes:
– Remote configuration of the MD720
– Diagnostics and maintenance functions using AT commands
– Process data connections between stations with TIM modules
The partner for the remote connection can be an analog modem, an ISDN modem or a
GSM modem.
● Controlling the MD720 using AT commands
You can control the MD720 from a locally connected application or manually with a
terminal program connected locally.
CP 1243-8 IRC
Operating Instructions, 06/2015, C79000-G8976-C385-01
Accessories
C.2 Modems
127