Preface Although CC-Link has performed well in the Chinese market, with numerous widespread applications and partners, comprehensive information about CC-Link is relatively scarce. As a technology incorporating the latest fieldbus advancements, CC-Link boasts advanced technical performance and distinctive features. It is necessary to gradually introduce CC-Link's technology and applications to a wider range of users, partners, and engineering professionals in China. This will allow more industry professionals to understand CC-Link's technology and provide valuable reference for the development of fieldbus technology in China. I. Background of Open Fieldbus CC-Link Technology and CLPA In November 1996, Mitsubishi Electric and several other companies developed, announced, and opened the fieldbus CC-Link based on the concepts of "multi-vendor equipment environment, high performance, and low wiring," officially launching this new multi-vendor, high-performance, and low-wiring field network to the market for the first time. In 1997, it received the Outstanding Technical Achievement Award from the Japan Electrical Manufacturers' Association (JEMA). CC-Link is short for Control & Communication Link. In short, CC-Link is a field network that enables simultaneous high-speed transmission of control and information data at 10Mbps in industrial control systems. CC-Link boasts outstanding advantages such as superior performance, wide application, ease of use, and cost savings. As an open fieldbus, CC-Link is the only bus system originating in Asia, and its technical characteristics are particularly well-suited to Asian thinking habits. In 1998, automotive companies such as Mazda, Isuzu, Yamaha, GM, and Suzuki became CC-Link users, and CC-Link rapidly entered the Chinese market. Sales exceeded 170,000 nodes in 1999, reached 720,000 nodes in 2001, and accumulated to 1.5 million by 2001, demonstrating rapid growth and a market share exceeding 15% in Asia (according to a survey by the US industrial control research firm ARC). It has received high praise from customers in Asia, Europe, America, and Japan. To make it easier for users to select and configure their own CC-Link systems, the CC-Link Partner Association (CLPA) was established in Japan in November 2000. The main responsibility is the global promotion and adoption of CC-Link. To ensure a unified global promotion, the CLPA (CC-Link Association) has established numerous offices worldwide, located in the United States, Europe, China, Taiwan, Singapore, South Korea, and other countries and regions, responsible for promoting and supporting CC-Link users and members in various aspects in different regions. CLPA currently has seven executive council members: Woodhead, Contec, Digital, NEC, Panasonic Electric Works, IDEC, and Mitsubishi Electric. As of the end of April 2002, CLPA had over 250 member companies worldwide, including several from mainland China such as Zhejiang University Control System and CUTE Software. II. CC-Link Communication Principles CC-Link's underlying communication protocol follows RS485. Please refer to the diagram below for specific communication methods. [align=center]Diagram: Communication Principles[/align] CC-Link provides two communication methods: cyclic transmission and instantaneous transmission. Generally, CC-Link primarily uses a broadcast-polling (cyclic transmission) method for communication. The specific method is as follows: the master station sends refresh data (RY/RWw) to all slave stations, while simultaneously polling slave station 1; slave station 1 responds to the master station's polling (RX/RWr) and informs the other slave stations of this response; then the master station polls slave station 2 (without sending refresh data at this time), slave station 2 responds and informs the other slave stations of this response; and so on, repeating in a loop. Please refer to the following diagram for the data transmission frame format during broadcast-polling. This method has a very high data transmission rate. In addition to the broadcast-polling method, CC-Link also supports instantaneous communication between the master station and local stations, and smart device stations. The instantaneous communication volume from the master station to the slave station is 150 bytes/data packet, and the instantaneous communication volume from the slave station to the master station is 34 bytes/data packet. Please refer to the following diagram for the data transmission frame format during instantaneous transmission. It can be seen that instantaneous transmission does not affect the cyclic scanning time of broadcast polling. All communication processes and protocols between master and slave stations are controlled by the communication LSI-MFP (Mitsubishi Field Network Processor). Its hardware design ensures CC-Link's high-speed and stable communication. [align=center]MFP Structure Diagram[/align] III. CC-Link's Superior Performance Generally, industrial control networks are divided into 3 to 4 layers: the upper management layer, the control layer, and the component layer. The component layer can be further subdivided into the device layer and the sensor layer. CC-Link is a network primarily based on the device layer, but it can also cover the higher-level control layer and the lower-level sensor layer. 1. CC-Link Network Structure The general system structure of the CC-Link fieldbus is shown in the figure: [align=center]Figure: CC-Link System Structure[/align] Generally, a single-layer CC-Link network consists of one master station and 64 slave stations, connected via shielded twisted-pair cables using a bus connection. The master station in the network is a Mitsubishi Electric FX series or higher PLC or computer. Substations can be remote I/O modules, special function modules, local PLC stations with CPUs, HMIs, inverters, servo systems, robots, and various measuring instruments, valves, CNC systems, and other field instruments. To enhance system reliability, a redundant network system with a master station and a backup master station can be used. Using gateways from third-party manufacturers can also enable connections from CC-Link to ASI, S-Link, Unit-wire, and other networks. 2. CC-Link Transmission Speed ​​and Distance CC-Link boasts high-speed data transmission, reaching up to 10Mbps. Its data transmission speed gradually decreases with distance. The specific relationship between transmission speed and distance is shown in the table below. [align=center]Table: Correspondence between Transmission Speed ​​and Distance[/align] There are currently several types of CC-Link repeaters: one is the T-type branch repeater AJ65SBT-RPT, where the distance doubles with each additional repeater. A maximum of 10 repeaters can be used in a single network layer. The second type is the optical repeater AJ65SBT-RPS or AJ65SBT-RPG, which uses fiber optic cable for extension, making it suitable for environments prone to interference. Optical repeaters must be used in pairs; the extension distance between each pair of AJ65SBT-RPS is 1 kilometer, with a maximum of 4 pairs; the extension distance between each pair of AJ65SBT-RPG is 2 kilometers, with a maximum of 2 pairs. The third type is the spatial optical repeater AJ65BT-RPI-10A/AJ65BT-RPI-10B, which uses infrared wireless transmission and is used in situations where cabling is inconvenient or the connected equipment location may change. Spatial optical repeaters must also be used in pairs, with a distance between them not exceeding 200 meters. There are also repeaters for easy wiring and gateways and bridges for connecting to other networks. CC-Link provides 110-ohm and 130-ohm terminating resistors to prevent transmission quality degradation due to external environmental interference, such as parity errors, when the bus distance is long and the transmission speed is high. 3. CC-Link Enables High-Speed, High-Capacity Data Transmission. CC-Link offers two communication modes: cyclic transfer and instantaneous transfer. Each memory station transmits 24 bytes of data in a cyclic transfer, with 8 bytes (64 bits) used for bit data transmission and 16 bytes (4-bit RWr, 4-bit RWw) used for word transmission. A physical station occupies a maximum of 4 memory stations, so a single physical station can transmit 96 bytes of data in a cyclic transfer. For the entire CC-Link network, the maximum capacity of each link scan in a cyclic transfer is 2048 bits and 512 words. When the cyclic transfer data volume is insufficient, CC-Link provides an instantaneous transfer function, which can transmit 960 bytes of data to the target station via commands. With 64 remote I/O stations connected at a communication speed of 10 Mbps, the link scan time for cyclic communication is 3.7 milliseconds. Stable and fast communication speed is CC-Link's greatest advantage. 4. CC-Link's Rich Functionality: 1) Automatic Refresh and Station Reservation Functions: CC-Link automatically refreshes network data from the network module to the CPU, eliminating the need for dedicated refresh commands. Reserved stations can be pre-configured during system setup. When these devices are connected to the network, CC-Link automatically recognizes them and integrates them into the system without reconfiguration, maintaining continuous system operation and facilitating system design and debugging. 2) Comprehensive RAS Functions: RAS stands for Reliability, Availability, and Serviceability. Features include automatic offline functionality for faulty substations, automatic return after repair, station number overlap checking, faulty invalid station detection, network link status checking, and self-diagnostic functions, providing a reliable network system and helping users restore the network system in the shortest possible time. 3) Interoperability and Plug-and-Play Functions: CC-Link provides partner manufacturers with data configuration documents describing each type of product. This document, called a memory mapping table, defines the storage units (addresses) for control signals and data. Partner manufacturers then develop CC-Link compatible products according to these mapping tables. Taking the analog I/O development worksheet as an example, in the mapping table, bit data RX0 is defined as "read ready signal," and word data RWr0 is defined as analog data. Products of the same type manufactured by different companies, A and B, have completely identical data configurations. Users do not need to consider the differences between companies A and B in programming and usage. Furthermore, if a user switches to a product of the same type from a different company, the program requires minimal modification. "Plug and play" connection is possible. 4) Loop and Instantaneous Transmission Functions: CC-Link offers two communication modes: loop communication and instantaneous communication. Loop communication involves continuous data transmission across the network. Data of different types from different stations can be shared, and this is automatically handled by the CC-Link core chip MFP. Instantaneous communication is used when the data volume in loop communication is insufficient, or when a larger amount of data (maximum 960 bytes) needs to be transmitted. One-to-one communication can be achieved using dedicated instructions. 5) Excellent Noise Resistance and Compatibility: To ensure good compatibility across multiple manufacturers' networks, consistency testing is crucial. Typically, only the interface portion is tested. Moreover, CC-Link's consistency testing program includes noise immunity testing. Therefore, all CC-Link compatible products have a high level of noise immunity. As far as we know, only CC-Link can achieve this. In addition to the product's own excellent noise immunity, fiber optic repeaters provide the network system with more reliable and stable noise immunity. To date, there have been no reports of system malfunctions caused by noise. IV. Application Features Because CC-Link can directly connect to various flow meters, solenoid valves, temperature controllers, and other field devices, it reduces wiring costs and facilitates changes to wiring designs; through repeaters, it can maintain a high-speed communication speed of 10M within 4.3 kilometers, thus it is widely used in various field control fields such as semiconductor production lines, automated conveyor lines, food processing lines, and automotive production lines. In China, CC-Link has also been used in many places. Its application features are summarized as follows: a) Facilitates the construction of a simple, low-cost control network. As a fieldbus network, CC-Link can not only connect various field instruments but also connect various local control station PLCs as intelligent device stations. When communication between local control stations is minimal, CC-Link can be used to create a simple PLC control network at a significantly lower cost compared to a dedicated control network. For example, consider the air conditioner testing production line at Qingdao Haier. Each testing station on this line uses an independent PLC (Mitsubishi Electric FX2N PLC) to control its testing tasks. To enable management to monitor the operation of each station in a timely manner, CC-Link is used to connect the independent control stations into a network. A host computer connected to the master station (Mitsubishi Electric A1SJHCPU) monitors the entire testing line. Compared to traditional RS485 communication, CC-Link offers longer communication distances, faster speeds, and a competitive price. Furthermore, its powerful RAS (Real-Time Analysis) functionality allows the host computer to monitor the operation of each field testing station, promptly identifying anomalies and network connectivity issues. If a PLC station malfunctions, it automatically disconnects without affecting other stations, and automatically reconnects after repair. b) Facilitates the construction of cost-effective redundant networks. In some fields, high system reliability is required, often necessitating the establishment of a master station and a backup master station to form a redundant system. Although CC-Link is a field-level network, it offers many functions found in higher-level networks, such as the ability to configure a master station and a backup master station. Due to its low cost, it offers high cost-effectiveness. For example, this function of CC-Link was used in the Yinchuan thermal power plant project. Both the master station and the backup master station use Mitsubishi Electric's Q2ASH CPU, connected to two remote input stations and remote output stations via CC-Link. When both the master station and the backup station are working normally, the master station controls the remote stations; when the master station fails, the backup master station automatically takes over system control and operates as the master station, preventing system downtime. c) Suitable for sites with dispersed control points and narrow installation areas. In building monitoring systems, such as gas monitoring systems, there are many corresponding detection points, which are relatively dispersed. In addition, high-rise buildings often minimize the size of mezzanines and vertical passageways to achieve economical design. Using CC-Link field network to connect discrete remote I/O modules, a single network layer can control up to 2048 points in 64 locations, with a total extension distance of up to 7.6 kilometers. The small input/output modules, measuring only 87.3x50x40mm, are suitable for installation in extremely confined spaces. Shanghai Xipai Industrial Co., Ltd.'s Measurement and Control Department successfully developed and commercialized the "FLD Fieldbus-based Gas Leakage Monitoring System" in the first half of 1998, using CC-Link field network communication. This product has been successfully applied in projects such as Shanghai Pudong International Airport. d) Suitable for direct connection to various field devices. Because CC-Link is a fieldbus network, it can directly connect to various field devices. For example, in the Hebei Grand Theatre project, numerous frequency converters were used. Previously, the common method for connecting frequency converters was through output contacts, analog signals, or RS485 communication. For example, when using analog signals, for each frequency converter, the PLC needs one channel of an analog signal module corresponding to it. If one module with 8 channels of D/A conversion is used, connecting 40 frequency converters would require 5 such modules. However, if CC-Link is used, one connection module can be installed on the PLC to connect 42 frequency converters. Using CC-Link to connect frequency converters not only allows for a larger number of connections but also has a longer communication distance than RS485. Furthermore, it has overall monitoring and diagnostic functions for network communication and is convenient for communication programming—all advantages that RS485 communication cannot match. V. Practical Application Examples (I) The Meizhou tobacco re-drying production line monitoring system uses CC-Link to build its on-site working network and monitors the production equipment through CC-Link. The system is currently in operation and working well. The mechanical parts of the production line use tobacco machinery produced by Beijing Changzheng Dao Control Engineering System Integration Co., Ltd. and Kunming Shipbuilding Equipment Group Co., Ltd., and the two companies use Mitsubishi Electric's industrial control products for system integration. Moreover, the system cost is significantly lower than previous imported production lines. The following is a brief introduction to the control system, and its production line system overview is shown in Figure 4-1. [align=center] Figure 4-1 Meizhou Tobacco Factory System Diagram[/align] The production line consists of six process sections: pre-treatment, leaf sorting and air distribution, dust removal, leaf drying, stem drying, and pre-compression packaging. Each section is controlled by a Mitsubishi Q2ASCPU-S1 PLC station. These six PLC stations communicate with each other via the MELSECNET/10 network and are connected to a host computer via Ethernet through the PLC in the pre-treatment section. Two host monitoring computers use IFIX configuration software to monitor the entire production line online and store the data collected from the field into a database. One workstation computer can organize, analyze, store, and output the data in the database. The engineer station computer can read the programs of all six control stations on site, monitor their operating status, modify the programs, or perform remote control. The PLC control station is equipped with a CC-Link module A1SJ61QBT11, which connects several frequency converters and a HMI (Human Machine Interface) A985GOT. The HMI allows for various input controls and output monitoring, and can directly control the frequency converters. For ease of explanation later, we will simplify the system. Assume the CC-Link module is inserted in the first slot to the right of the CPU module, with a starting address of H0000. One frequency converter and one HMI are connected via a fieldbus. The HMI controls the frequency converter's start/stop, frequency adjustment and monitoring, acceleration adjustment and monitoring, load current monitoring, and reset. The specific PLC internal resources used are as follows: X20: Start; X21: Stop; X22: Input frequency; D201: Store set frequency value; X23: Monitor frequency; D101: Store monitored frequency value; X24: Monitor current; D100: Store monitored current value; X25: Input acceleration; D203: Store set acceleration value; X26: Monitor acceleration; D103: Store monitored acceleration value; X27: Reset. When using CC-Link connection, both hardware and software settings are required. 1. Hardware: Shielded twisted-pair cables are used to connect each control device via a bus. The DA/DB lines of the twisted-pair cable are two signal transmission lines, DG is the ground wire, and SLD is the shielding layer, as shown in Figure 4-2. Then, the station number switch and transmission speed switch (knob or toggle type) on each station are set. The frequency converter is set to station 1, and the HMI is set to station 2. A communication speed of 5Mbps is used. Note that all devices must operate at the same speed; otherwise, the L.ERR (communication error) light will illuminate. [align=center] Figure 4-2 Hardware Connection Diagram[/align] 2. The following software settings are required: I. Configure CC-Link. This can be done by writing an initialization program or by configuring it on the parameter setting screen. (The latter is only supported by higher version products.) II. Write the corresponding communication program. The configuration will be explained below. Before CC-Link runs, the main station needs to be configured to specify how many substations are connected to the system, what each station is, etc. Then write the initialization program; if using the parameter setting screen, it is shown in Figures 4-3 and 4-4. [align=center] Figure 4-3 Figure 4-4[/align] The communication program mainly writes the data exchange required for inverter communication. The HMI connects to CC-Link, and there are two communication methods. One is a cyclic communication method, which requires simple programming of the communication content on the PLC side. The other is an instantaneous communication method, which only requires specifying the software components to be monitored directly on the HMI side, but the required communication time is slightly longer. Therefore, for some information with low real-time requirements, a simple instantaneous transmission method can be used. In this system, the human-machine interface mainly uses instantaneous transmission. In the setting screen of the soft component, the network number and station number of the soft component to be monitored are directly specified in the "Network" option. Here, the HMI is specified to monitor station 0 of network 1, which is the master station. See Figure 4-5 below for specific settings. [align=center] Figure 4-5 HMI settings[/align] For the above-mentioned PLC internal resources X20/X21…D100/D103/D201, etc., the corresponding settings are made on the human-machine interface according to this method. (II) When designing the automation project of the pump room of Shenzhen Bijia Mountain Water Plant, Shenzhen Water Group Kaitianyuan Automation Co., Ltd., after analysis and comparison, considered that the original factory had partially implemented workshop PLC control. After price and performance analysis and comparison, it was determined that the open fieldbus CC-LINK fieldbus product was selected as the main control device. The control hardware system structure diagram is shown in Figure 4-6. [align=center]Figure 4-6 Hardware Structure Diagram of the Control System for the Bijia Mountain Water Plant Pump Station[/align] In the diagram, the master station controls one water delivery pump, two vacuum pumps, and one drainage pump, monitoring and managing the entire pump station's CC-Link network, including: 1. Remote Offline: Automatically disconnecting malfunctioning remote modules or slave stations from the network. 2. Automatic Recovery: Automatically reconnecting malfunctioning remote modules or slave stations to the network once they recover. 3. Automatic Diagnosis: Checking hardware and system wiring status using self-test functions. 4. Network Monitoring: Storing network status in the CPU's registers. 5. Responsible for receiving vacuum pump start commands from the seven (slave) pumps, forwarding pump status data, effluent water quality data, and transmitting pump start commands issued by the plant's dispatch center. Slave stations 1-3 each monitor and control the operation of two water delivery pumps, receiving pump start commands from the master station and sending pump status data to the master station. Slave stations 4-7 monitor and control the power distribution room. This system monitors high-voltage power distribution (closing/opening, transformers, capacitor compensation) and monitors and controls low-voltage power distribution (closing/opening, transformers, DC power panels). Remote I/O stations collect some power distribution parameters. This application system is designed for equipment in the pumping station of the Bijia Mountain Water Plant of Shenzhen Water Supply Company. The most significant advantages of using CC-LINK fieldbus products are: (1) The network speed of the automatic control system in the pumping station reaches up to 2.5Mbps (at 100m), with fast data acquisition and short system response time, improving control accuracy and reliability. (2) The system's anti-interference capability is significantly enhanced. (3) Wiring is simple, and fault diagnosis and location are rapid. (4) The introduction of the control system greatly reduces the labor intensity of workers and improves production efficiency. (5) Automatic fault isolation. When a slave station or smart instrument fails, the system can automatically isolate this station without affecting the operation of the entire network. (6) Convenient system expansion. Adding stations or backup stations can be connected online to the network; simply set them as reserved stations. (7) Strong interconnectivity with other brands of equipment. This system connects CC-LIN to the MODBUS network, demonstrating stable inter-network connection performance and accurate and timely data transmission. It provides a solution to the problem of interconnecting equipment from different brands. The FCS mode adopted by this application system is more advanced and reliable than the previous DCS or PLCS modes. As time goes on, it is believed that the use of fieldbus mode in China's water supply industry will increase, and the successful application of CC-Link in the Shenzhen water plant provides valuable experience for the application of CC-Link in the water treatment industry. VI. CC-Link Technology Development Through the above introduction, we have gained a preliminary understanding of the characteristics and functions of CC-Link. Given the actual characteristics and functions of CC-Link, it is suitable for many control systems, and its own functions are constantly being improved and enhanced. The number of partner manufacturers that can connect to field devices is also constantly increasing, making it more beneficial for field applications. In the process of continuous progress and development of CC-Link technology, CLPA launched the CC-Link family of downstream products and the CC-Link/LT protocol in 2002, mainly used for the transmission and communication of switch data, making the overall structure of CC-Link more complete and robust, and further reducing its cost. In early 2003, CLPA announced the release of CC-Link V2.0, which increased system communication capacity eightfold compared to the previous version. In summary, CC-Link is an advanced, high-performance, widely applicable, easy-to-use, and low-cost open fieldbus with broad prospects for technological development and application in China.