Technical data

2.4 Configuring the Network
2.4.1 Configuring a SINEC L2 Network for RS-485
When configuring a purely electrical network the following values are
important:
➣
max. segment length
➣
max. number of stations
➣
max. length of the connecting cables
➣
cascading rules for SINEC L2 repeaters.
Fig. 2.5 shows the typical structure of a SINEC L2 network for RS-485,
comprising several segments connected by repeaters.
Owing to the frequency-dependent attenuation of the cable, the maximum
segment length depends on the data rate. Table 2.1 shows the maximum
segment lengths for a SINEC L2 bus cable.
Number of stations
The maximum number of addressable stations with SINEC L2 (and
PROFIBUS DIN 19245) is 127. A maximum of 32 stations are possible per
bus segment (stations and repeaters).
Connecting cables
The segment lengths indicated here can only be achieved when certain
frequency-dependent capacitances caused by the connecting cables to the
stations are not exceeded. It may be necessary to reduce the total length of
the connecting cables. (see Table 2.2).
B8976060/02 System Overview
2 - 23 Volume 1