78
shielded twisted pair cable, the longest communication distance is 9.6km (requires additional relay), and the
maximum length is 90km when using fiber optic cable.
The maximum cable length of each segment of Profibus-DP is related to the transmission rate. Different media,
different baud rates, and different distances that signals can be transmitted are shown in Table 7.
Table 7
：
Transmission rate and distance relationship table
Baud
rate
kbps/s
9.6
19.2 93.75 187.5 500 1500
3000
6000
12000
(Line A)
cable length
m
1200 1200 1200 1000 400 200
200
100
100
(Line B)
cable length
m
1200 1200 1200 600
200 Not
recommended
Not
recommended
Not
recommended
Not
recommended
Note: This transmission distance refers to the distance without repeaters (repeaters). In addition, the transmission
distance is a theoretical value, and the actual transmission distance is also affected by the on-site environment.
10.1.3 PROFIBUS-DP Bus network structure
PROFIBUS supports bus, star and tree topologies. A bus topology, as shown in Figure 1. The standard
Profibus-DP system can connect up to 127 stations (station numbers from 0 to 126, without repeaters). PROFIBUS
supports repeater connections. If a repeater is used, the cable length and the number of connected stations can be
increased.PROFIBUS
图 1
DP Bus topology
According to the EIA RS485 standard, in order to minimize cable reflection and ensure the noise level defined
on the data line, at each end of the data transmission cable, a terminating resistor connected as follows must be used
to terminate a network segment. The bus terminator is shown in Figure 2.
APM
APM
APM
APM
APM
Master
station
