Modbus Bus Coupler BK7350
Status display
power LEDs
Bus Coupler
Input for
power contacts
Power contacts
Fieldbus connection
Address selector
Configuration interface
Address selector
extended temperature range

BK7350 | Modbus Bus Coupler

ModbusThe BK7350 “Compact” Bus Coupler with compact housing connects the Modbus bus system to the modular, extendable electronic terminal blocks. One unit consists of one Bus Coupler, any number from 1 to 64 terminals and one end terminal. With the K-bus extension, up to 255 Bus Terminals can be connected.

The Bus Coupler recognizes the terminals to which it is connected, and performs the assignment of the inputs and outputs to the words of the process image automatically. The first input/output signal will be added to the first bit of a word (LSB), beginning from the left. The Bus Coupler adds further signals to the word. A clear separation is maintained between inputs and outputs. If the number of inputs or outputs is greater than 16 bits, the Bus Coupler automatically begins a new word.

Modbus has a line topology based on the RS485 interface. The Modbus protocol is published. The BK7350 supports the RTU and ASCII protocols. The baud rate is variable and can be set directly via the rotary selection switch on the Bus Coupler, i.e. without configuration software.

The Modbus Bus Coupler supports various Modbus functions that enable direct access to digital and analog signals. The BK7350 also supports the diagnostic Modbus function that enables faults to be detected and counted. In addition, the Bus Coupler diagnoses faulty or erroneous telegrams and respond to the controller with an error. The BK7350 enables broadcast access, which means that several Bus Couplers can be addressed simultaneously with a single telegram.

System data Modbus | BK7350
Number of I/O stations 99
Number of I/O points depending on controller
Data transfer medium screened, twisted copper cable 2 x 0.25 mm² (RS485)
Max. cable length 1,200 m
Data transfer rates 150 baud…38,400 baud
I/O communication types read/write access, optionally bit oriented or word oriented
Technical data BK7350
Number of Bus Terminals 64 (255 with K-bus extension)
Max. number of bytes fieldbus 512 byte input and 512 byte output
Digital peripheral signals 1,020 inputs/outputs
Analog peripheral signals 256 inputs/outputs
Protocol RTU/ASCII (default: RTU)
Configuration possibility by rotary switch or KS2000
Bus interface D-sub 9-pin, RS485
Power supply 24 V DC (-15 %/+20 %)
Input current 320 mA max.
Starting current 2.5 x continuous current
Recommended fuse ≤ 10 A
Current supply K-bus 1750 mA
Power contacts max. 24 V DC/max. 10 A
Electrical isolation 500 V (power contact/supply voltage/fieldbus)
Weight approx. 100 g
Operating/storage temperature -25…+60 °C/-40…+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/markings CE, UL, ATEX
Ex marking II 3 G Ex nA IIC T4 Gc
KS2000 configuration software for extended parameterisation
Cordsets cordsets and connectors
Modbus For further Modbus products please see the system overview