3.5 RS-485
M-Bus Master MultiPort 250L’s RS-485-connection can be used for M-Bus communication on an equal basis with the other
serial connections.
The following communication speeds can be used for M-Bus communication:
•
300 Baud 8E1
•
2400 Baud 8E1
•
9600 Baud 8E1
Maximum recommended cable length is 1,200 m.
The master’s integrated port controller makes sure that communication is only possible on one serial port at a time.
3.6 M-Bus Output
All meters in an M-Bus network are connected to M-Bus Output terminals 24 and 25. The master includes four sets of
connections coupled in parallel.
3.6.1 Current and voltage
Bus mark/space
41 V DC/28 V DC
Detection level, communication
7 mA
Detection level, collision
25 mA
Max. normal operating current
375 mA
Warning level, operating current
377 mA
- Overload LED flashes
Overload level, operating current
500 mA
- Overload LED is constantly illuminated
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