Introduction
18 ATM60 / ATM90 / KHK53
Dec 2021
At the bus connector or at the bus terminal block, a 5 V supply voltage is available for the bus
termination via external resistors. – See also Figure 4–4 (VP, DGND).
The maximum cable length depends on the transmission speed. The specified length can be
extended using repeaters. The use of more than 3 successive repeaters is not recommended.
Figure 4–5: Cabling (9-Pin D-Sub Connector) and Bus Termination.
The cores of the data cables are identified by 'A' and 'B' (terminals (3) and (8)). It is not defined
which core must be connected to a particular terminal on the bus terminal block. The handling,
however, must be identical throughout the system. The following allocations are used:
• Data line 'A' green
• Data line 'B' red
4.3.4 Profibus Cabling for RS485
Two basic cable types are available for copper-based Profibus DP networks. According to the
electrical
properties, they are called 'cable type A' and 'cable type B' (not to be confused with
the cores ‘A’ and ‘B’ at 4.3.3).
Cables of type A are the only permitted cables for new installations.
The following specifications relate to a cable of type A:
Parameter Cable properties type A
Wave impedance 135 ... 165 Ω
Distributed capaci-
tance
< 30 pF/m
Loop resistance < 110 Ω/km
Core diameter 0.64 mm
Core cross-section > 0.34 mm
2
• The cumulative length of all spurs is limited to
6 m
(depending on how the stations are ar-
ranged).
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