9
•
Vast array of systems and components available
•
Different types of bus topology: linear, star, and tree
Figure 3 - Bus topologies
4.1.3
Addressing
The M-Bus protocol provides two types of addressing modes to detect and communicate with the devices
connected to the bus
•
Primary addressing
: up to 250 primary addresses can be allocated within an M-bus system
(hexadecimal format). The primary address is normally allocated while setting up the units.
•
Secondary address
: the secondary address consists of 8 bytes and allows the allocation of any
number between 00000000 and 99999999. By default, the secondary address of the devices is the
same as the manufacturer serial number. Readings by secondary address while scanning the bus
allow the acquisition of the meters that support the “Wildcard” logic, the same that enables the
selection of a group of devices based on the section of their serial number.
4.1.4
Sizing the M-Bus System
Follow the instructions provided in the table to size the M-Bus system
Type of plant
Maximum
distance
Overall
cable
length
Cross-section
mm
2
Number
of
devices (slaves)
Max.
transmission
rate
Small
residential
buildings
350 m
1000 m
0.8 mm
250
9600 Baud
Large
residential
buildings
350 m
4000 m
0.8 mm
250
2400 Baud
64
9600
Small complex
1000 m
4000 m
0.8 mm
64
2400 Baud
