CC-Link IE Field
The CC-Link Partner Association (CLPA) is an organisation of manufacturers of CC-Link compatible products and users of CC-link technologies. The CLPA overseas and manages the CC-Link specifications and promotes the worldwide adoption of CC-Link technology for network communications in industrial automation.
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In industrial automation, there has been a progressive shift from proprietary communications to open networks. However many users have preferred to retain these proprietary networks due their superior performance and reliability.
In developing an open Industrial Ethernet for field level devices, the CC-Link Partner Association (CLPA) focused on reliability and higher performance than proprietary networks, but without compromising the openness of the network. The resulting CC-Link IE Field network is based on Ethernet technology (IEEE 802.3)
In addition to high throughput of control and communication data, the CLPA developed CC-Link IE technology to enable automation and plant engineers with little or no underlying knowledge of the Ethernet network configurations to maintain the system. Automated troubleshooting, flexible topologies, determinism and resistance to electrical noise have also been important criteria.
Many of the high network availability features from the original (and still compatible) CC-Link have also been integrated into CC-Link IE. These include automatic station bypass, and hot swap of network devices.
CC-Link IE field network has been developed to enable the easy transfer of data across networks with determinism and minimal latency. To achieve this, control data uses cyclic communication and a system shared memory, while messaging data uses transient/acyclic communication. Media access control for CC-Link IE Field level is by token passing.
In operation each controller exchanges data with all other controllers, recognises the condition of other controllers, and performs its own control actions. The CC-Link IE Field network performs cyclic communication at a communication speed at 1 Gbps. Therefore, the control data of each station can be updated in real time.
The shared memory communication model allows the users to easily realise real-time communications to read from or write to the memory without considering a connection between send and receive stations.
CC-Link IE assigns a portion of the transmission bandwidth for transient message communication between network stations for on-demand messages that do not require determinism. These messages do not affect the cyclic real-time operation of the network.
Any device connected to the network can send and receive data from the shared memory and therefore no specific CC-Link IE protocol knowledge is required. Importantly, this function enables users to communicate seamlessly from each station to all the stations, and this function has a benefit of creating a control program that is logically a single hierarchy network regardless of physical configurations of the network.
Unlike other industrial Ethernet networks, CC-Link IE Field delivers deterministic control communications without requiring the addition of Ethernet switches. This feature eliminates the hardware costs and engineering implementation costs of Ethernet switches. Also eliminated is the cost and need for developing communication statements to govern the flow of data.
By using this function, an error occurring in one station does not have a major impact on the entire system, and the error part can be minimised. Therefore, stable operation of the system can be maintained at all times.
A CC-Link IE Field network allows a highly flexible topology best suited to the needs of the particular application. These include star, line, ring and mixed star & line topology designs. Built-in network diagnostics provide cost reductions from installation, to operation and network maintenance.
One of the aims of CC-Link IE is to simplify the implementation and adaptation of Industrial Ethernet. The field network can be built to a topology decided by the physical layout the individual stations. When adding new ones, they can be connected freely either to a port on an existing station (for line topologies) or to a port on a layer 2 switch (for star topologies).
The physical layer and data link layer of CC-Link IE Field network apply Ethernet Technology. Commercial Ethernet cables, layer 2 switches and network analyzers can be used. So the availability of materials and selectivity of equipment for the network installation, adjustment, and troubleshooting are simplified. The media used is Cat5E cable and RJ45 connectors.
Ethernet compatible devices such as barcode readers or RFID scanners are seamlessly connected using SLMP over the TCP/IP. Since the SLMP is a simple client and server type protocol it can be easily implemented into firmware for 100Mbps Ethernet devices from third party vendors, and then connected to CC-Link IE field via an Ethernet adaptor. The device can then be accessed across the network.