Interbus Bus Coupler BK4020
Power LEDs
Bus Coupler
Input for
power contacts
Power contacts
Fieldbus signal input
Fieldbus signal output
Configuration interface

BK4020 | Interbus Bus Coupler

InterbusThe BK4020 “Economy plus” Bus Coupler connects the Interbus bus system to the electronic terminal blocks, which can be extended in modular fashion. One unit consists of one Bus Coupler, any number of up to 64 terminals and one end terminal.

With the K-bus extension technology, the BK4020 allows the connection of up to 255 spatially distributed Bus Terminals to one Bus Coupler. The “Economy plus” coupler supports all Beckhoff system Bus Terminals and can process 512 bit digital inputs and outputs per slave. The number of analog channels is limited by the Interbus protocol to a maximum of 32 input and 32 output channels. The transmission rate is 500 kbaud. Slave devices can be spaced up to 400 m from each other as the fieldbus interface acts as repeater. The overall length of an Interbus ring is limited to 13 km.

The identification code and the length code are determined by the Bus Coupler automatically after starting, depending upon the connected Bus Terminal, and are read out by the master. It is not necessary to parameterise the slave.

The Bus Coupler recognises the connected terminals and automatically generates the affiliations of the inputs/outputs to the bytes of the process image. The first input/output signal is inserted in the first bit of one word (LSB), beginning from the left. The Bus Coupler inserts further signals in this word. Inputs and outputs are clearly separated.

Interbus has been established as an open fieldbus system since 1987. Interbus has a ring structure, and up to 256 stations can be operated in a ring. Data transmission takes place at 500 kbaud. Due to the efficient data transmission, sensor and actuator data can be transferred over great distances.

The Interbus coupler works with the protocol chip SUPI3 and supports the extended diagnostics of the Interbus master. Byte-by-byte addressing in the master is supported as from generation G4.

System data Interbus | BK4020
Number of I/O stations 256
Number of I/O points 4,096
Data transfer medium LiYCY 3 x 2 x 0.22 mm²
Max. cable length max. 400 m
Data transfer rates 500 kbaud
Data transfer time approx. 1 ms in the case of 10 modules for 32 bit input and output each
Technical data BK4020
Number of Bus Terminals 64 (255 with K-bus extension)
Max. number of bytes fieldbus 64 byte input and 64 byte output
Digital peripheral signals 512 inputs/outputs
Analog peripheral signals 32 inputs/outputs
Configuration possibility via KS2000
Data transfer rates 500 kbaud
Bus interface 2 x D-sub plug, 9-pin, plug and socket with screening and vibration lock
Power supply 24 V DC (-15 %/+20 %)
Input current 70 mA + (total K-bus current)/4, 500 mA max.
Starting current 2.5 x continuous current
Recommended fuse ≤ 10 A
Current supply K-bus 1750 mA
Power contacts 24 V DC max./10 A max.
Electrical isolation 500 V (power contact/supply voltage/fieldbus)
Weight approx. 170 g
Operating/storage temperature 0…+55 °C/-25…+85 °C
Relative humidity 95 %, no condensation
Vibration/shock resistance conforms to EN 60068-2-6/EN 60068-2-27
EMC immunity/emission conforms to EN 61000-6-2/EN 61000-6-4
Protect. class/installation pos. IP 20/variable
Approvals CE, UL, Ex
KS2000 configuration software for extended parameterisation
Cordsets cordsets and connectors
Related products  
BK4000 Interbus Bus Coupler for up to 64 Bus Terminals
Interbus For further Interbus products please see the system overview