Benefits of CC-Link IE compared to Profinet
Network bandwidth and network load
Currently, PROFINET uses 100Mbit and has limited transmission bandwidth available for communication. This means that it may not be possible to share all process data on the network. . This could be a limitation for Industrie 4.0 and IIoT applications as bandwidth is critical to handle the increasing amount of data. PROFINET runs best with a network load below 20%. A network load higher than 50 % should be avoided. From 50 % on counter measurement are needed to reduce the information volume on the network. Asynchronous (transient) messages have an impact on network load, speed and performance. Prioritised messages disturb communication traffic and risk causing lower priority messages to be lost in the worst case.
Gigabit bandwidth provides CC-Link IE with practically unlimited communication capacity. Transient, (acyclic) and cyclic (deterministic) information have separate communication channels within the CC-Link IE networks. The cyclic information is completely separated from transient information. This means increasing or decreasing amounts of transient information has no impact on control functions.
PROFINET usually works in star configuration with a point to point configuration. This ensures that no other station can disturb the communication traffic between two points. This allows non-deterministic types of PROFINET to operate more reliably. However, a star configuration means higher costs for wiring, installation and maintenance due to the additional cables and switches required. Some of the switches may have to be managed in order to handle traffic correctly. During set up, all network stations need to know who their neighbours are, i.e. who they are communicating with. This means a lot of initial configuration work and hence engineering time. This has also led to a small industry based on PROFINET debugging, analysis and optimisation. This shows that the total cost of ownership will increase on bigger installations to get it and keep it up and running.
In contrast to this, CC-Link IE offers line, tree or star topology or a mixture. The use of switches is not mandatory, since stations have two ports and support daisy changing at any point. All stations are connected to the main communication trunk and get all information. They are managed by their individual network address. Ring topology allows running a redundant network. Separate ring configuration is needed for electrical reflection suppression on the network.
Adding or removing stations to or from a network may need to happen when the network is up and running or in idle mode due to station failures, etc. System specialists who have a deep knowledge of the application and of PROFINET itself are required in these cases. All nodes need information of who their neighbours are, what are the communication channels and how they may interfere with each other. If the network configuration is changed due to a station being added or removed, then this information needs to be updated. Hence downtime may be increased while these updates are made and the new configuration established on the network.
This may also lead to higher engineering costs during the development and debugging phases while this information is determined and configured.
This aspect makes the system inflexible for Industrie 4.0, as it is more difficult to respond to a quickly changing production environment.
CC-Link IE allows adding or removing of stations within the running network without any trouble to the existing network. The master is in contact with all stations in each cycle. Hence any changes will be immediately recognized as devices are connected or disconnected to the network. The master can be configured to determine what actions are taken for given events to achieve the necessary functionality for the network. An Event during running mode could be a maintenance case or adding a new station into the network architecture and define the action (e.g., alarm or stopping of network) of each station during the event.
Flexibility is not a favorite topic for PROFINET: it needs a pre-determined communication map, which indicates what information is to be transmitted from node to node. The neighbourhood setting needs accurate planning, initialization and setting. Huge sets of documentation describe how to configure a PROFINET System for best performance. Furthermore it is very important how the stations cooperate with each other. After all settings are done the system is nearly frozen during the information download.
CC-Link IE offers tremendous flexibility. All information goes through all nodes unmodified and is stored in the master’s central memory. From there the updated information will be available in the next cycle. All stations receive same information independently of where they are connected to the network. This means the topology can be changed from line to tree or segments of it. Once a station is connected to any point on the network, the communication is up and running. The action taken when connecting or disconnecting each station to the network can be individually set. These actions can be an alarm, stopping the network or ignoring and continuing normal communication. Ring topology with its redundancy support needs additional settings to avoid reflections on the network.
Network initial setup
The initial setup for when a new PROFINET network is planned needs to be very carefully initiated, planned and set up. In particular, it may be a special challenge to try and foresee which data and functionality will be needed in the future. A PROFINET network setup needs a stable, forecasted and very well planned environment. Small changes later on need extra effort and a lot of work. This means the planner’s skills have to be very specialised on the application and functionality and also needs to know in detail how the system is working and what the best techniques to use are. This may limit a company’s ability to respond to a growing, innovative and dynamic process landscape.
In contrast to this CC-Link IE offers a clear and transparent structure for configuration. Once set, all parameters are unambiguous and determined by the engineering tool. Adding stations is easy thanks to the clear structure. The remaining architecture is unaffected by any changes on particular stations.
Network initial setup
PROFINET has no built-in network diagnostics. There are two main options to perform this. The first is to use switches, which are located between all nodes, devices, etc., to observe the data flow. In the case of malfunctions, error codes will be transmitted, which will be read and understood at a higher level, which can react on these issues in the appropriate way.
Another possibility is to use passive diagnostics. This sends data streams throughout the network and collects information with port mirroring and Test Access Points (TAP). The test results need also to be analysed to produce further actions for maintenance, which means further effort for troubleshooting and configuration.
In addition as a kind of active diagnostics with a user program in the master controller, faulty modules can be detected and the status information can be read and interpreted with much effort.
A CC-Link IE master is in continuous dialog with each station at any given time. All data are stored in the bit map, which displays a complete set of production data at each state of . This can be regarded as a kind of digital twin. This gives full transparency from the master to all stations and the complete network at any time. The token and information sent back from the stations delivers information for diagnostics and is implemented from the very beginning for use within the engineering tool. This helps to setup, maintain and improve the network without any additional tools, effort or additional expenses. The diagnostic function is a mandatory feature of CC-Link IE Field. This also explains why the comprehensive array of third party diagnostic tools that are available for PROFINET are not available for CC-Link IE.
Maintenance effort for PROFINET is relatively high and also needs attention during operation. Communication and network load might vary a lot and delay control functions. The maintenance needs to ensure that the communication is up and running as well as limiting the network load to max. 20%.
A network load already above 50% risks causing malfunctions and hence delays control functions. This means real-time communication is risky. PROFINET IRT addresses this with special hardware in the master, slaves and switches and other connected hardware to prioritise real time network traffic. While this may lower the maintenance effort, it also means that PROFINET IRT is no longer using standard Ethernet. Moreover, PROFINET I/O and RT cannot offer this capability.
CC-Link IE is nearly maintenance free. The communication channels for transient and deterministic information are strictly separated from each other. Each station has a fixed memory area in the master for writing and reading. This means observing and correcting network behaviour is usually not required. The available diagnostic tool shows the status at any time, so usually planned interventions are not needed. Finally, consideration of bandwidth is not required, as performance is guaranteed for all devices on the network.