PC Control / Profi Control 645-12M Instruction Manual pdf - Kuhnke

PROFIBUS hardware installation
B.1.1.2. T-junctions
Up to 500 kbit/s
Max. 0.3 m per T-junction
1500 kbit/s
The total branch line capacity is to be smaller than 0.2 nF.
The resulting total length of all branch lines is 6.6 m.
3000 ... 12000 Mbit/s
Although allowed, T-junctions should be avoided. The total
branch line capacity is to be smaller than 0.05 nF. The resulting
total length of all branch lines is 1.6 m.
Integrate a series inductance in the connector to reduce
line noise. One practical solution is to install the inductances
in the connector (bus node or bus terminator):
RxD/TxD-P
L
L
PROFIBUS -> PROFIBUS ->
L
L
RxD/TxD-N
Take the following series inductance as an example for a
typical connected capacity of a bus station (connector, line
length to RS-485 driver, RS-485 driver, components, etc.):
L = 100 nH
The capacity of the bus station is taken into account when
calculating the inductance value. Thus, pulling out the plug
may cause maladjustments which may have a negative impact
on the bus.
B - 2