Siemens SIMATIC NET PROFIBUS User Manual

3-8

PROFIBUS Networks SIMATIC NET

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

Table 3-6

Possible Segment Lengths

Segment Length for Cable Type

Transmission Rate
in Mbps

– 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

3

100 m

100 m

6

100 m

100 m

12

100 m

100 m

When planning segments for transmission rates from 3 Mbps to a maximum of 12
Mbps, the following factors must be taken into account:

S

To attach DTEs to bus segments, only the bus connectors permitted for 12
Mbps or the BT12M bus terminal can be used.

S

The maximum length of a segment must not exceed 100 m.

S

The maximum number of bus attachments (nodes, OLMs, RS-485 repeaters,...)
in one segment is restricted to 32.

S

To attach a programming device or PC via a tap line, only the “SIMATIC S5/S7
connecting cable, 12 Mbps, order no. 6ES7901-4BD00-0XA0” can be used.

If several bus connectors are used at electrically short distances (in other words,
the cable length between adjacent connectors is less than 1 m)  (for example,
several slaves in one cubicle), avoid disconnecting several bus connectors at the
same time for longer periods. Disconnecting more than one bus connector does
not necessarily mean errors but may well reduce the reliability (immunity to noise)
of a segment.