10
Smart Infrastructure
A6V11742346_en--_a
2019-10-01
M-bus
Address
M-bus uses two types of addresses to recognize devices:
●
Primary addressing: Up to 250 primary addresses can be assigned to a M-bus system.
The primary address is normally assigned during device commissioning. Pure primary
addressing is not possible if more than 250 devices are read on the M-bus network.
●
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
devices (slaves)
Max.
transmission
rate
Small residential
buildings
350 m
1000 m
0.8 mm
2
250
9600 baud
Large residential
buildings
350 m
4000 m
0.8 mm
2
250
2400 baud
64
9600 baud
Small
developments
1000 m
4000 m
0.8 mm
2
64
2400 baud
Large
developments
…3000 m*
5000 m
1.5 mm
2
64
2400 baud
Direct vicinity
…5000 m*
7000 m
1.5 mm
2
16
300 baud
Point-to-point
connection
…10000 m*
10000 m
1.5 mm
2
1
300 baud
*Shielded cabling required at a distance in excess of 1000 m (see EN13757-2 appendix E).
Signal specification
M-bus
Condition
Minimum
Typical
Maximum
Measuring unit
Number simple
M-bus loads per
segment
WTX631-
GA0090
0
-
250
-
Transmission
rate
C
Segment
≤ 382 nF
300
2400
9600
baud
Bus power
(Master)
WTX631-
GA0090
30
39
42
R
Bus current
(master)
WTX631-
GA0090
0
-
375
mA
