Addressing

M-bus uses two types of addresses to recognize devices:

  • Primary addressing: Up to 250 primary addresses can be assigned to an M-bus system. The primary address is normally assigned during device commissioning.
  • Secondary addressing: Secondary addressing consists of 8 bytes and permits the assignment of any number. In the default setting, the secondary address for a device normally matches the serial number issued by the device manufacturer. The assignment prevents address conflicts on the bus.

Bus expansion

Plant type

Maximum distance

Total cable length

Cable cross-section

Number of M-bus devices (slave)

Max. transmission rate

Small residential buildings

350 m

1000 m

0.5 mm2

500
(250 per line)

9600 baud

Large residential buildings

350 m

4000 m

0.5 mm2

500
(250 per line)

2400 baud

64

9600 baud

Small developments

1000 m

4000 m

0.5 mm2

64

2400 baud

Large developments

3000 m*

5000 m

1.5 mm2

64

2400 baud

Direct vicinity

5000 m*

7000 m

1.5 mm2

16

300 baud

Point-to-point connection

10000 m*

10000 m

1.5 mm2

1

300 baud

* Use shielded cables at distances greater an 1000 m
(see EN13757-2 Appendix E).

Signal specification

M-bus

Condition

Minimum

Typical

Maximum

Measuring unit

Number of simple M-bus loads per M-bus IoT-Gateway

WTV776-HB6035

0

-

20

-

Transmission rate

CSegment ≤ 382 nF

300

2400

9600

baud

Bus power

WTV776-HB6035

24

40

42

V

Bus current

WTV776-HB6035

0

 

30

mA