16
of 175
4.2.1 Parameter value
Characteristic impedance in
Ω
135 to 165 for 3 to 30 Mhz
Effective capacitance
< 30 pF/m
Loop impedance (
Ω
/km)
< 110
Wire diameter (mm) *)
> 0.64
Wire cross-section (mm2) *)
> 0.34
*) The wire cross-sections used must be suitable for the connection options on the bus connector.For
cable type A, the maximum cable lengths for a bus segment depend on the transfer rate.
4.2.2 Transfer Rate
Transfer rate
Max. bus segment length
9.6 ... 93.75
kBaud
1200 m
187.5
kBaud
1000 m
500
kBaud
400 m
1500
kBaud
200 m
3000 / 6000 / 12000
kBaud
100 m
Commercially available connectors allow the incoming data cable to be connected directly to the
outgoing data cable in the connector. This avoids stubs, and the bus connector can be connected to
the bus or disconnected from the bus at any time without interrupting data traffic. These connectors
include a bus termination that can be switched in or out. To avoid line reflections, connectors
containing integral series inductors should be used to compensate for the capacitive load of the
station. This is essential for transfer rates > 1.5 MBaud.
Diagram 1: Wiring of bus lines with bus termination