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1-8 Series 90™-30 CPU with Embedded PROFIBUS Interface – November 2004 GFK-2334A

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

PROFIBUS uses linear bus architecture with active bus termination at both ends. Devices

in a PROFIBUS network connect directly to the bus cable or indirectly via stub lines.

Master

Series 90-30 PLC with

PROFIBUS Master CPU

Series 90-30 PLC

with PROFIBUS Slave

Module

Slaves

Stub w/

Slaves

Bus

Termination

Bus

Termination

Sample PROFIBUS Network

A PROFIBUS-DP network may have up to 125 slave stations (addresses 0-125 are valid

addresses). The Master must consume one of the valid addresses to create a PROFIBUS

system. The bus system must be sub-divided into individual segments to handle this many

participants. These segments are linked by repeaters, which condition the serial signal to

allow connection of segments. In practice, both regenerating and non-regenerating

repeaters may be used. Regenerating repeaters 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 network. Each participant on the bus must have a unique station address.

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