SERCOS News - Issue 1 - 2008

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4 Sercos-Inside The Real-Time Ethernet Magazine Block I/O - easy integration of I/O signals in SERCOS III mum cycle times of only 31.25 µs (the blink of an eye takes approx. 330,000 µs), the fast transfer of the information is guaranteed. Also, the architecture enables direct communication between the executing units (slaves) so as to keep reaction times down to a minimum. To optimise the network, SERCOS III does not require expensive additional network components, such as switches or hubs. The integrated network functions ensure that TCP/IP packets can also be transmitted next to the real-time data. The reliability is increased by a robust design, a ring structure of the lines against the consequences of a cable break, as well as the secured data transmission via a certified safety protocol. The data is protected automatically, which require no additional hardware. Since October 2007, the SERCOS III real time Ethernet solution has been part of mandatory IEC standards. The vote for SERCOS III as the international standard was unanimous. This reflects the worldwide importance of the SERCOS interface. SERCOS II was already standardized worldwide. In parallel to standardization of third generation SERCOS, IEC decided to incorporate the existing IEC 61491 SERCOS II standard into the new IEC 61158/ 61784-1 standards series. The SERCOS drive profile was included in the new IEC 61800-7 standard. All three SERCOS generations are now part of the IEC standards. 2 million SERCOS nodes are currently installed worldwide, and the IEC decision is goods news for SERCOS developers and users. The evolution of SERCOS is characterized by continuity and a clear migration path. The common interface ensures interoperability between products from different manufacturers which use the same standardized interfaces, commands and synchronization methods. More than 80 different manufacturers now offer SERCOS-enabled products. At the field level, which is where communication between individual drives, sensors and controllers takes place, SERCOS III real time functions guarantee the required level of precision. Connectivity to higher level control systems is extremely simple. Companies gain direct access to data at the lowest production level, and every Ethernet-enabled computer can be connected to a SERCOS III port without any additional hardware or software. The computer can link into corporate TCP/IP communications without putting production-level runtime performance at risk. This works because in addition to real time communications, SERCOS III has a channel for non real time information (NRT). The completely transparent integration of real time and non real time data enables users to operate a large mix of devices on the same network. In contrast to other Industrial Ethernet solutions, SERCOS III does not require additional hubs and switches, and it does not use any additional protocols. Connectivity is completely transparent, because Ethernet systems without a SERCOS III ID are automatically allocated to the NRT channel. A 100 Mbit data rate supports data exchange between many devices in parallel without compromising the integrity of real time communications. Transparent integration of real time and non real time data allows companies to completely rethink their systems strategies. SERCOS III brings two worlds Highest precision - with cycle times till 31,25µs together. All nodes speak the same language. Different modules can even share the same cables without compromising integrity and reliability. SERCOS III, like previous SERCOS generations, is based on the field-proven hardware synchronization solution as it offers the greatest reliability. Every module comes with a special logic module which coordinates the SERCOS nodes with each other. This eliminates any need for additional expensive con trol points in the form of hubs and switches, and the network coordinates itself automatically. Synchronization is therefore one of the basic features of every SERCOS solution, not a feature which has to be added on each time with additional modules or protocols. At the same time the cycle time of 31.25 μs in real-time mode does not mean that one individual module would take up the complete range for itself alone. Instead, it is possible for up to eight drives in Motion Control applications to be supplied with 8 bytes of cyclical data and for them to send the same number of diagnoses as well. This is sufficient for the most demanding tasks currently conceivable in mechanical engineering. Even high-precision CNC machines have minimal cycle times of 500 µs. Thanks to the greater efficiency of SERCOS techno logy it will not be long before there will be no applications which would make it necessary to have a higher network speed. Moreover, Fast Ethernet also offers sufficient reserves for TCP/IP communication in production – especially because SERCOS is very efficient in the use of resources. Flexibility is a success factor in production and Industrial Ethernet is a protocol which allows planning and production to be coordinated with each other with-
The Real-Time Ethernet Magazine 5 Motion and I/O: Together with SERCOS III SERCOS III coupler for the WAGO-I/O-SYSTEM • Full support for Sercos III V. 1.20 protocol and SERCOS safety based on CIP safety • Compatible with the SERCOS III I/O profile • Additional I/O fieldbus no longer required • I/O nodes synchronous with motion cycle • Redundancy possible through ring topology • 100 Mbit/s • Cross communication • Additional standard IP channel www.wago.com
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SERCOS News - Issue 1 - 2008

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