Siemens Industry Online Support
Siemens AG
Entry type: Application example Entry ID: 25545680, Entry date: 08/21/2017

Sending and receiving SMS messages with serial CP or CM and MODEM MD720

  • Entry
  • Associated product(s)
A SIMATIC station (S7 300, S7 400 or S7 1500) is to send alarm messages, warning messages or important information on the system status autonomously via SMS to service staff or a control center. In addition, the SIMATIC station is also to receive and interpret messages.

To connect a SIMATIC S7-300, S7-400, S7-1500, ET 200S or ET 200SP to a GSM network, the GPRS/GSM MODEM MD720 is connected to the serial interface of a communications processor (CP340, CP341, CP441-2, 1SI, CM PtP).

The download file "Library" consists of the library  "LMD720_V13" for STEP7 V13 and the library "LMD720_V14" for STEP7 V14.

The appropriate function block "LMD720_SmsXxxx" from the library is used for data exchange between a SIMATIC S7-CPU and a serial communication module or a serial communication processor and the MODEM MD720.

The solution presented here offers the following advantages:

  • The "LMD720_SmsXxxx"  user block provides you with immediately usable functions for your applications. 
  • By using the MODEM MD720 you can send alarm messages or other important system information to the service staff with low cost.

This library is only valid for the MODEM MD720. The application examples for MD720-3 are available in the archive.

 Documentation (1,6 MB)
 Registrierung notwendig  Library (2,5 MB)

 Registrierung notwendig  Wireless Signaling and Switching via SMS with serial CPs/CMs and the MD720-3 GPRS/GSM Modem (STEP7 V13) (12,3 MB)
 Registrierung notwendig  Wireless Signaling and Switching via SMS with serial CPs/CMs and the MD720-3 GPRS/GSM Modem (STEP7 V5.5) (3,2 MB)

Further Information
The following links provide additional information on sending SMS messages with SIMATIC controllers.

Signaling and Switching via SMS with S7-1200 and CP 1242-7 GPRS V2 (Set 32)
Wireless Signaling and Switching per SMS with S7-1200 Controller and MD720-3 (Set 25)
Sending and Receiving SMS Messages via a SCALANCE M Router

Last Changes
New library for the MODEM MD720.

Security information
In order to protect technical infrastructures, systems, machines and networks against cyber threats, it is necessary to implement – and continuously maintain – a holistic, state-of-the-art IT security concept. Siemens’ products and solutions constitute one element of such a concept. For more information about cyber security, please visit