A field bus is a bus system that connects sensors and actuators to a control computer (PLC) for information exchange. Each manufacturer has designed its own communication mechanisms for its fieldbus so that all sensors and actuators can exchange information without interference. Most field buses are based on the so-called master-slave method.

Advantages of fieldbus technology:

  • Reduced installation effort: less cabling, smaller, simplified control cabinets
  • Reduced troubleshooting in the event of a fault
  • One cable for digital/binary and analog signals
  • Protection against interference with analog values
  • Self-diagnosis of the automation system - for example in case of errors in the sensors/actuators
  • Easier extension, respectively simple addition of sensors/actuators

Feldbus Protocol standards

LAPP offers a range of different bus components to suit the different technical requirements that a network in your application environment may have to fulfil and the bus systems which are used as a result. Below we will briefly look at the key protocol standards and consider simple S/A cabling (which connects sensors and actuators with one another) as well as more complex fieldbuses (which establish a network between decentralised peripheral devices and controller devices).

LAPP’s range includes copper cables for all the bus systems described. However, fibre optic cables would essentially also be conceivable. Simply get in touch if you would like a consultation!


Sensor/actuator cabling

If you need to connect conventional sensors and actuators to superordinate network levels, LAPP can offer you copper S/A cables as well as a range of different bus components. All products from LAPP’s UNITRONIC® range which are ideally suited for this task come with the inscription “SENSOR”, which makes them easy to identify.

AS-i (Actuator Sensor Interface) is the world’s only standardised fieldbus system for the lower process level. Using just one port and only one cable with two cores, this simple connection system can network up to 31 sensors and actuators/AS-i modules with the controller level. In this context, the AS-i cable is responsible not only for exchanging data, but also for supplying power to the slaves. A cyclic transfer rate of ≤ 5 ms can be achieved here with a cable length of 100 m. As a result, this open industry standard (which is not tied to a specific manufacturer) enables fast, efficient cabling in industrial automation, which ultimately reduces costs.

The AS International Association e.V. promotes the expansion and standardisation of the AS-i protocol standard. LAPP is a member of this association and plays an active role in further developing the standard.

Copper cables and components in accordance with the AS-i standard
The AS-i-compliant cables from LAPP’s UNITRONIC® range have the inscription “ASI”, which indicates at a glance that they are suitable for AS-i applications.



More complex network cabling

PROFIBUS® (Process Field Bus) is a standard for fieldbus communication, and one of the world’s leading fieldbuses nowadays. It enables data to be exchanged cyclically between devices on the lower field level (decentralised peripheral devices, slaves) and higher-level controller units (central masters). It has now become a key communication protocol used in manufacturing technology as well as process technology and engineering. The master–slave system can use both twisted pair cables as well as fibre optic cables.

If higher speeds are required, the successor development PROFINET® with its Ethernet capability can be used. 

Lapp Kabel is a member of the user organisation PROFIBUS Nutzerorganisation e.V. (PNO) and plays an active role in further developing PROFIBUS®.

The following two variants of PROFIBUS® are primarily used. 

Fieldbus communication in manufacturing technology can be handled using either a mono-master set-up or a multi-master system (where several masters are connected to a bus). The masters query input information from the slaves at cyclic intervals and return output information. Different versions of the PROFIBUS® DP system are available:

  • DP-V0 for cyclic communication,
  • DP-V1 additionally for acyclic communication,
  • DP-V2 additionally for isochronous real-time functionality, use of timestamps, and slave-to-slave communication.

PROFIBUS® DP offers a transfer rate of 12 Mbit/s and can combine up to 126 devices (masters and slaves) in a network.

PROFIBUS® PA is used for communication in process automation applications. As the power is limited, PROFIBUS® PA is ideally suited for use in potentially explosive atmospheres. The transfer rate of 31.25 kbit/s allows for long cable paths and a high degree of resistance to electromagnetic interference.

The names of the PROFIBUS®-compliant products from LAPP’s UNITRONIC® range (for cables) and EPIC Data range (for connectors) include the designation “BUS DP” for PROFIBUS DP and “BUS PA” for PROFIBUS PA.     

Copper cables and components in accordance with the PROFIBUS® DP standard

Copper cables in accordance with the PROFIBUS® PA standard


The CANopen standard has taken the CAN (Controller Area Network) fieldbus system that was originally developed for the automotive industry and has expanded it to include a communication profile. This makes CANopen an open protocol standard for use not only in automation technology but also many other industries, such as medicine, railways, etc., predominantly in Europe.

In the serial CAN system the data is exchanged in the form of telegrams on both a cyclic and event-driven basis, and the exchange is managed via the first two layers of the OSI model. The network participants with equal status independently transfer their messages to the bus at a secure transfer speed of up to 1 Mbit/s, over a cable length of 40 m. In the process, data is exchanged in real time.

In the higher-level CANopen system, an application layer is integrated in order to provide a communication profile. By means of standardised interfaces, this profile is able to individually address the device and application profiles of the device classes used in the network. As a result, the communication profile controls which telegrams are used to exchange which device data.

CANopen is maintained by CiA (CAN in Automation).

Copper cables and components in accordance with the CANopen standard
The CANopen-compliant components from LAPP’s UNITRONIC® range have the inscription “BUS CAN” (for lines and patch cables) and “CAN” (for connectors), which indicates at a glance that they are suitable for CANopen applications.

In Asia, CC-Link is the leading open industry standard with pronounced deterministic characteristics, used for exchanging data between the controller and manufacturing level. It is available in different variants. In the standard variant, CC-Link is a fieldbus system enabling a data transfer rate of up to 10 Mbit/s over a total cable length of 100 m, as well as real-time communication with up to 64 devices in the network. If the network speed is lower the transfer distance can be extended to up to 1,200 m. This means CC-Link is also suitable for large-scale applications. The simple structure of this standard is sufficient for many automation technology tasks. This network technology is also increasingly being used in Europe, as CC-Link-compatible products from different manufacturers can be integrated very easily.

You can find more information about the Ethernet-based variant of CC-Link under CC-Link IE.

CC-Link is standardised by the CLPA (CC-Link Partner Association) user organisation.

LAPP is a member of the CLPA and plays an active role in further developing CC-Link.

Copper cables and components in accordance with the CC-Link standard
The CC-Link-compliant cables from LAPP’s UNITRONIC® range have the inscription “CC”, which indicates at a glance that they are suitable for CC-Link applications.