Communication extension card
-5-
communication baud rate is required to be higher than 187.5 kbps, strictly follow the wiring standards
stipulated by Siemens.
2.
Repeaters
A maximum of 32 stations (including the master station) can be connected to each fieldbus segment. If
the number of stations to be connected to a fieldbus segment exceeds 32, you need to use repeaters
to connect the fieldbus segments. Generally, the number of repeaters connected in series cannot
exceed 3.
Note:
No station address is provided for repeaters, but they are calculated as stations.
Terminal
Repeater
Repeater
1
1
2
31
30
2
3
30
31
……
……
Figure 2-2 Repeaters
3.
Transmission rates and maximum transmission distances
The maximum length of a cable depends on the transmission rate.
describes the transmission rates and corresponding transmission distances.
Table 2-2
Transmission rates and corresponding transmission distances
Transmission rate (kbps)
A-type wire (m)
B-type wire (m)
9.6
1200
1200
19.2
1200
1200
93.75
1200
1200
187.5
1000
600
500
400
200
1500
200
-----
12000
100
-----
Table 2-3 Transmission wire parameters
Parameter
A-type wire
B-type wire
Impedance (Ω)
135–165
100–130
Capacitance of a unit length (pF/m)
< 30
< 60
Circuit resistance (Ω/km)
110
--------
Wire core diameter (mm)
0.64
> 0.53
Sectional area of wire core (mm
2
)
> 0.34
> 0.22