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The line between Industrial Automation and Process Control is becoming increasingly blurred as industry umbrella groups try to provide a turnkey architecture for all applications. It is not just a political wish on the part of individual lobbies. Unification is now backed by advanced software tools sitting on a layer of newly available hardware processing power spun out from the world of enterprise IT.ODVA Executive Director Katherine Voss advocates the Common Industrial Protocol as a unified network solution capable of integrating control, configuration, information, safety, synchronisation and motion in a proven and future-proof network architecture.

The network landscape is changing in manufacturing automation, driven both by evolving user requirements and by the rapid adoption of internet technology. Manufacturers don't want just control of their manufacturing processes any more: they want information about their processes and they want it anywhere, any time! To meet these needs, network architectures in manufacturing are moving away from hierarchal organisation towards an application-based form.

To integrate control with information and internet technology, manufacturing automation requires a network architecture designed for plant floor-to-enterprise connectivity and TCP/IP routing capability. Industrial Ethernet will exist somewhere in this architecture, but economical deployment hinges on using off-the-shelf technology wherever possible, which means the use of industrial Ethernet compatible with a standard Ethernet infrastructure (switches, routers, etc).

The ODVA, through its technology mix of Common Industrial Protocol (CIP), Ethernet, TCP/IP and the Internet, can provide users with a network architecture that meets the application requirements for control, configuration, information, safety, synchronisation and motion in manufacturing processes. This network architecture will integrate manufacturing networks with enterprise-level Ethernet networks and the Internet that will become increasingly important in the future.

CIP Networks are designed to be media-independent, and to work in conjunction with Internet Protocol routing. In addition, it promotes a producer-consumer network technology. Thus, a CIP Network architecture lets users optimise the physical implementation of the network for the application while eliminating the need for gateways to connect networks with dissimilar upper-layer protocols.

EtherNet/IP, CIP, Internet and Ethernet standards provide a pure Ethernet solution for control networks says the ODVA

CIP network adaptations

CIP, and its network adaptations - DeviceNet, EtherNet/IP, and ControlNet - are open technologies. This openness is achieved in two primary ways. Firstly, the specifications for CIP and its network adaptations are managed through multi-vendor collaboration who assign their intellectual property output to the CIP network specifications.

Secondly, the use of the specifications to make and sell products based CIP networks technologies requires users of the specifications to meet a consistent set of standards defined as 'user responsibilities'. The result of this openness is that we can claim CIP and CIP Networks to be the only standards-based open technologies in the industry: they provide true interoperability and stability, and there are no hidden vendor agendas or reliance on one specific vendor.

CIP networks started shipping in 1994 with DeviceNet. Even this initial implementation of CIP took advantage of COTS technology by using the same CAN 2-wire bus used in automotive control systems for its physical layer. EtherNet/IP was released in 2000 as an adaptation of CIP to TCP/IP technology on a standard Ethernet IEEE-802.3 physical layer.

EtherNet/IP

Ethernet IEEE-802.3 technology provides a specification of the physical media, defines a simple frame format for moving packets of data between devices, and defines a set of rules determining how network devices respond when two devices attempt to use a data channel simultaneously. However, by itself, the Ethernet specification lacks the necessary communication protocol features need to implement fully functional networks. TCP/IP provides these features and, although it will run on alternate physical media, it has become inextricably linking with Ethernet.

As far as an industrial Ethernet solution is concerned, many of the current flavours eliminate the benefits of Ethernet as an open, off-the-shelf technology by instead ultimately delivering a proprietary solution that will restrict users in their ability to realise the full potential of Ethernet and Internet technologies in manufacturing automation. EtherNet/IP, the other hand, is simply the adaptation of CIP to the TCP/IP suite and Ethernet IEEE-802.3 standards. CIP, running on EtherNet/IP can coexist with any other protocol one may find running on top of the standard TCP/UDP Transport Layer, while EtherNet/lP can coexist with any of the other CIP networks optimised for device level installations and/or high speed determinism.

In short, EtherNet/IP - CIP on Ethernet Technology - provides a pure Ethernet solution for control networks and enables both internet and enterprise connectivity, anywhere, anytime.

DeviceNet provides users with the ability to distribute and manage simple devices throughout their architecture

Benefits of CIP networks

Very few, if any, manufacturers design and implement every aspect of their enterprise networking in one go, and even fewer never make changes or upgrades to the original networks. This makes scalability a vital requirement for the present network environment. In addition, users want the ability to select the networks that best address their needs at various levels of networking and in various areas of the enterprise.

CIP networks provide the required flexibility and scalability. The ability to originate a message on one CIP network such as DeviceNet, and then pass it to another CIP network such as EtherNet/IP, with no presentation at the application layer, sets CIP networks apart from others.

CIP is a producer/consumer-based model, rather than a traditional source/destination model. Producer/consumer networks make more efficient use of bandwidth. When a message is introduced onto the network, it is identified not by its destination address, but by its connection ID. Multiple nodes may then consume the data to which the connection ID refers. As a result, if a node wants to receive data, it only needs to ask for it once in order to consume the data each time it is produced. And, if a second (third, fourth, etc.) node wants the same data, all it needs to know is the connection ID to receive the same data simultaneously with all other nodes. On the other hand, using the source/destination model, nodes receive only the packets that contain their destination node number. If more than one node needs the same data, it must be transmitted multiple times which is inherently inefficient.

Future extensions

ODVA introduced two major extensions to the CIP specification last year, one for safety implementations and the other to provide precise synchronisation of network devices.

The certification of CIP Safety by TÜV in accordance with IEC 61508 up to SIL3 paves the way for CIP safety networks and systems. Because the safety protocol only runs in the end-nodes, standard and safety devices will be able to co-exist on the same wire. Standard devices will not interfere with the functions of the safety devices, while safety devices will support both standard and safety connections. This leads directly to seamless bridging and routing between CIP networks.

Being based on a producer/consumer model, CIP networks already provide inherently stable synchronisation between devices. However, for applications where absolute time synchronisation between devices is vital, ODVA has added a time synchronisation extension to the CIP specification.

CIP Sync is based on the recent IEEE-1588 standard Precision Clock Synchronisation Protocol and provides true time synchronisation between devices. Synchronisation accuracy between two devices of less than 500ns can be achieved over a conventional 100Mbps Ethernet system with a switch-based architecture. And unlike the event synchronisation model typically used, the CIP Sync approach allows efficient use of network bandwidth while maintaining a high degree of synchronisation.

CIP Motion is a further extension which will provide users with real-time, deterministic closed loop motion control for multi-axis controller-to-controller synchronisation and controller-to-drive communication by extending CIP Sync to motion applications such as electronic line shafting, camming and phase lock loop control. Compatibility will be maintained with the standard Ethernet infrastructure such that HMI, I/O, and Motion can coexist on same network.

Summary

ODVA has four main objectives:

• To accelerate the overall adoption rate of CIP based technologies in vendor products;
• To strengthen the customer guarantee implied by ODVA trademarks to users;
• To deliver CIP based solutions for key vertical markets;
• To make CIP the best-in-class protocol for as many applications as possible.

Katharine Voss is executive director, ODVA.
www.odva.org