The Open Modbus/TCP software solution developed by Siemens

The Open Modbus/TCP software solution developed by Siemens enables easy integration of the entire Simatic automation family in heterogeneous or third-party system landscapes. The different systems are linked up via Industrial Ethernet by means of an open communications protocol. This allows existing systems to be expanded or modernized with Simatic system technology gradually and cost-effectively.

The increasing use of Ethernet-based data communication in both industrial and office environments requires the modernization or expansion of existing automation systems. The result is often a heterogeneous system landscape. Linking it up to a powerful higher-level system necessitates the use of open, preferably standardized communications protocols. The Open Modbus/TCP solution developed by Siemens is based on Modbus, a protocol that is used all over the world and is already supported by many manufacturers. The communications protocol is an open Internet draft standard that has already been incorporated in the IETF (Internet Engineering Task Force). As a result of this disclosure, any manufacturer or user can implement this protocol.

Open Modbus/TCP now also supports central processing units with Profinet capability (PN-CPUs) and thus the entire range of Simatic automation devices. There are three Modbus variants available for integrating different Simatic systems: the Modbus block for communications processors is suitable for Simatic S7-300 and S7-400 systems. For Modbus communication, a CP343-1 or a CP443-1 communications processor is needed as well. The Modbus block for central processing units with Profinet capability is used to link up Simatic S7-PN CPUs and ET200S-PN CPUs. For Modbus communication in this case the integrated Profibus interface is used. For Simatic S7-400H systems, the Modbus block with redundancy functionality is used and, for communication purposes, a CP443-1 communications processor is needed for each subsystem as well.

The range of functions performed by all Modbus variants supports server mode, client mode and conformance class 0 with the function codes 3 and 16. The block with redundancy functionality also makes it possible to establish a communications link that is redundant and therefore fail-safe at the same time. For communication between Simatic stations and other Modbus nodes, native TCP connections that are based on the standard functions of the Simatic S7 library are set up. All Modbus blocks have multi-instance capability. Configuration is carried out with the standard Simatic STEP 7 tool. A software wizard is also available for configuring the Modbus blocks for Profinet CPUs.

The Siemens Industry Sector (Erlangen, Germany) is the world's leading supplier of production, transportation and building systems. Integrated hardware and software technologies combined with comprehensive industry-specific solutions enable Siemens to enhance the productivity and efficiency of its customers in industry and infrastructure. The Sector comprises six Divisions: Building Technologies, Industry Automation, Industry Solutions, Mobility, Drive Technologies and Osram. In fiscal 2007 (ended September 30), Siemens Industry generated sales of approximately EUR40 billion (pro forma, unconsolidated) with around 209,000 employees worldwide.

With the business activities of Siemens VAI Metal Technologies, (Linz, Austria), Siemens Water Technologies (Warrendale, Pa., U.S.A.), and Industry Technologies, (Erlangen, Germany), the Siemens Industry Solutions Division (Erlangen, Germany) is one of the world's leading solution and service providers for industrial and infrastructure facilities.