Table 7: M-Bus protocol rules (bus topology)
Category
Rules
64
350 m (1,148 ft)
4,000 m (13,123 ft)
(2 x 0.8 mm [20
AWG], shielded,
resistance <
30Ohms)
9,600
250
350 m (1,148 ft)
1,000 m (3,281 ft)
(2 x 0.8 mm [20
AWG], shielded,
resistance <
30Ohms)
38,400 64
350 m (1,148 ft)
1,000 m (3,281 ft)
(2 x 0.8 mm [20
AWG], shielded,
resistance <
30Ohms)
Cable
Twisted pair cable (shielding optional)
Termination
No termination
1
Unit load is a defined standby current. A device is permitted a current drain of one unit load by default but may
consume more if it is shown at the device (as an integer) and in documentation.
2
Use M-Bus Repeaters to increase the length and the number of unit loads permissible.
Table 8: KNX protocol rules
Category
Rules and Maximums
General
No restrictions in topology
Number of Devices Depends on chosen topology and cable type.
Line Length and
Type
Twisted pair cable recommended; length depends on cable resistance,
capacitance, number devices, position of devices, and communication speed.
Cable
Copper, solid and stranded wires with outer sheath, one- or two-twisted pair;
0.8 to 1.0 mm (20 to 18 AWG)
Screen is required and must cover the entire diameter.
Drain wire: Diameter minimum 0.5 mm (26 AWG)
Termination
No termination
Manufacturer's
Quality
Management
System
At least ISO 9002
25
NAE55/NIE55 Installation Guide
