Siemens SIMATIC NET PROFIBUS Benutzerhandbuch

3-4

PROFIBUS Networks SIMATIC NET

6GK1970-5CA20-0AA1 Release 2 05/2000

If you do not attach the LAN cable directly to the bus connector (for example,when
using a PROFIBUS bus terminal), you must take into account the maximum
possible tap line length!

The following table shows the maximum permitted lengths of tap lines per bus
segment:

Table 3-2

Lengths of the Tap Lines per Segment

9.6

 –

 

93.75 Kbps

96 m

32

32

187.5 Kbps

75 m

32

25

500 Kbps

30 m

20

10

The following maximum segment length can be implemented with the SIMATIC
NET PROFIBUS LAN cable:

Table 3-3

 Possible Segment Lengths

Segment Length for Cable Type

Transmission Rate
in Kbps

– FC Standard Cable
– FC Robust Cable
– FC FRNC Cable
– FC Food Cable 
– FC Underground Cable
– SIENOPYR–FR Marine Cable

– FC Trailing Cable
– PROFIBUS Flexible Cable 
– PROFIBUS Festoon Cable

1.500

  200 m

  200 m

Each attachment of a node to the LAN cable represents a capacitive mismatch that
has no effect at lower transmission rates. At a transmission rate of 1.5 Mbps,
however, problems can arise due to these mismatches if the following guidelines in
terms of type, number and distribution of node attachments are not adhered to.