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Functions and Parameters
12.14 E8: Standard Communication
12.14.1 Modbus Protocol
Brief Introduction
EFC x610 frequency converters provide standard RS485 communication inter-
face to realize the communication between the master and slaves via Modbus
protocol. With the help of a PC, a PLC or an external computer a 'single master /
multiple slaves' network control can be realized (setting of frequency control
command and running frequency, modification of parameters, monitoring of fre-
quency converter running status and error messages) to address the specific re-
quirements of applications.
User parameters of the frequency converter can be written via com-
munication interface for 150,000 times.
Protocol Description
Protocol introduction
Modbus is a master / slave protocol. Only one device may send commands in
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the network at a particular time.
The master station manages message exchange by polling the slave stations.
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Unless being approved by the master station, no slave station may send mes-
sage. In case of an error during data exchange, if no response is received, the
master station will query the slave stations absent from the polling.
If a slave station is unable to recognize a message from the master station, an
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exception response will be sent to the master station.
Slave stations cannot communicate with each other but through the master's
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software which reads data from one slave station and sends them to another.
There are two types of dialogs between the master station and the slave sta-
tions:
– The master station sends a request to a slave station and waits for its re-
sponse.
– The master station sends a request to all slave stations and does not wait
for their response (broadcasting).
Bosch Rexroth AG R912005854_Edition 09
Rexroth Frequency Converter EFC x610
Series
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