INTERBUS introduction

The INTERBUS fieldbus system has become established in all sectors and applications, and the number of devices used in different applications is increasing continuously. INTERBUS is an international global standard. However, we are regularly asked about the basic principles of INTERBUS and INTERBUS-capable equipment.







INTERBUS INTERBUS is one of the most widely used fieldbus system internationally. In order to be able to judge the function of INTERBUS and its advantages, the basic technical principles have to be known. In the following sections, the INTERBUS basics are therefore explained.

The INTERBUS fieldbus system INTERBUS is an open fieldbus system for modern automation applications that integrates the complete process periphery with all common controls. Via the serial bus cable, sensors and actuators can be networked, machines and system components controlled, manufacturing cells networked and higher-level systems, e.g. control rooms, integrated. Topology and configuration in terms of topology, INTERBUS is a ring system, i.e. all devices are actively integrated in a closed transfer route. Each device regenerates the incoming signal and passes it on. A special feature of INTERBUS systems compared with other ring systems is that both the data outward line and the return line are carried within a single cable through all devices. This results in the physical appearance of a line or tree structure. Physical addressing from the bus master In contrast to other systems, data assignment to the individual devices is not via allocation of a bus address with dip or rotary switch in the individual devices, but automatically via the physical position of the device in the system. In terms of the installation effort and serviceability of the system, this plug-and-play functionality is a crucial advantage.

The problems and fallibility that can originate from the necessity to set a device address manually during installation and maintenance are often underestimated. In terms of topology, INTERBUS is a ring system, i.e. all devices are actively integrated in a closed transfer route. Each device processes the incoming signal and passes it on to the next device. In the INTERBUS system, both the supply and return lines are integrated in a single cable and run through all devices. This results in the physical appearance of a line topology. The bus master has an outgoing main line, from which subsystems for structuring the complete system can be formed. In this way, the bus system can be customised for every application.

 Topology determines flexibility Up to 512 devices can be connected to the INTERBUS master-slave system. The last device automatically closes the ring. Point-to-point connection Due to the point-to-point connection, no termination resistors have to be installed. The system can be flexibly adapted to user requirements by adding or removing devices. A variety of topologies can be configured. Branch bus terminals create branches that enable devices to be added or removed. The gateways between the bus segments allow subsystems to be switched on or off, thus enabling work on the subsystem to be carried out without repercussions, for example in the event of a fault or for system extensions.


 Introduction to the system

     The INTERBUS system is configured as a data ring with a central master/slave access procedure. It has the structure of a spatial distributed shift register. Each device, with its registers of different length, is part of the shift register ring. The master pushes data through the ring serially. The use of the ring structure offers the option of sending and receiving data simultaneously. The two data directions of the ring are located in a single cable. Each INTERBUS system device has an ID register (identification register). This register contains information about the module type, the number of input and output registers, and status and error conditions. The INTERBUS system basically knows two operating modes: - The ID cycle, which is carried out for the initialisation of the INTERBUS system and on demand. In the ID cycle, the coupling module reads the ID registers of all devices attached to the bus system and uses this information to build the process image. - The data cycle; this is the actual duty cycle dealing with the data transmission. In the data cycle, the input data are transferred from the registers to the coupling module, and the output data from the coupling module the devices.



System configuration and device types

 The INTERBUS club has a large number of different ID codes. Apart from 6 ID codes, Phoenix Contact has assigned these ID codes to couplers with digital and analog periphery. The manufacturer can therefore not be identified via the ID code. (Detailed commentary in Chapter "ID code and ID length"). The handling of the BK4xx0/BC4xx0 INTERBUS couplers does not differ from the equipment of other manufacturers.