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1-4 Series 90™-30 PROFIBUS Slave Module User's Manual – August 2004 GFK-2121A
1
Data bandwidth Demands on PROFIBUS Communications Systems
Amount of Data Transmission
Duration
Transmission
Frequency
Management level Mbytes Hours/Minutes Day/Shift
Cell level Kbytes Seconds Hours/Minutes
Field Level Bytes Several 100
microseconds to 100
milliseconds
10 to 100 milliseconds
Actuator sensor level Bits Microseconds to
milliseconds
Milliseconds
Network Topology
A PROFIBUS-DP network may have up to 127 stations (address 0-126), however address
126 is reserved for commissioning purposes. The bus system must be sub-divided into
individual segments to handle this many participants. These segments are linked by
repeaters. The function of a repeater is to condition the serial signal to allow connection of
segments. In practice, both regenerating and non-regenerating repeaters may be used.
Regenerating repeaters actually condition the signal to allow increased range of the bus.
Up to 32 stations are allowed per segment and the repeater counts as a station address.
A specialized “link” segment consisting only of optical fiber modem repeaters may be used
to span long distances. Plastic fiber optic segments are typically 50 meters or less while
glass fiber, optic segments may extend several kilometers.
The user assigns a unique PROFIBUS station address to identify each master, slave, or
repeater in the entire network. Each participant on the bus must have a unique station
address.