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Figure 9 Configuration of pull high/low resistor for the RS-485 port
2.3.4 PROFIBUS Connection
The PROFIBUS interface of the GW-7552-B / GW-7552-M is a DB9 female
connector. The connector uses the standard Profibus 9 pin assignment. It is
recommended to use a standard PROFIBUS cable and connector (DB9 male).
As with every serial bus the rate of safe data transmission in a Profibus network
decreases with increasing distance between master and slave. Table 7 shows the
transmission rate and range for a cable with the following properties:
1. Impedance :135~165Ω
2. Capacity : lower than 30 pF/m
3. Loop resistance : lower than 110Ω/Km
4. Wire diameter : greater than 0.65mm
5. Core cross-section : greater than 0.34mm
Table 7 Transmission rate decreasing with increasing transmission distance
Transmission Rate(Kbps)
9.6; 19.2; 45.45;93.75
187.5
1500
3000; 6000; 12000
In order to minimize the reflection effect of signal transmission, both ends (first
node and last node) of a PROFIBUS segment needs to be equipped with an
GW-7552-B / GW-7552-M PROFIBUS/MODBUS GATEWAY User Manual (Version 1.60, May/2017) PAGE: 13
500
Transmission Distance per Segment (meter)
2
1200
1000
400
200
100
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