Technical data

Network configuration
3.1 Configuring electrical networks
PROFIBUS Network Manual
System Manual, Edition 04/2009, C79000-G8976-C124-03
43
Table 3- 2 Length of spur lines per segment
Number of nodes with spur line
length of ...
Transmission speed Max. length of spur
lines per segment
1.5 m or 1.6 m 3 m
9.6 to 93.75 kbps 96 m 32 32
187.5 kbps 75 m 32 25
500 kbps 30 m 20 10
3.1.3 Segments for a transmission speed of 1.5 Mbps
Transmission speed 1.5 Mbps
The following maximum segment length can be implemented with the SIMATIC NET
PROFIBUS cable:
Table 3- 3 Possible segment lengths
Segment length for cable type
Transmission speed in
kbps
- FC standard cable
- FC standard cable IS GP
- 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
- PROFIBUS torsion cable
1,500 200 m 200 m
Node attachments at 1.5 Mbps
Each attachment of a node to the bus cable represents a capacitive mismatch that has no
effect at lower transmission speeds. At a transmission speed 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.
Weighting factors
To be able to define permitted configurations, a method is necessary with which the attached
components can be evaluated in terms of their capacitive bus load. This is achieved by
assigning weighting factors to the components (see table below).
PROFIBUS interfaces implemented as 9pin D-sub female connectors (CPs, OLMs...), do not
have their own weighting factors. These are already taken into account in the values listed in
the table.