12 Communication Protocols
12.1 Introduction
Fv provides standard RS485 communication port to realize the communica‐
tion between the master station and the slave station via Modbus or
PROFIBUS protocols. With the help of a PC, an SPS or an external computer
a “single master/ multiple slaves” network control can be realized (setting of
frequency control command and running frequency, modification of function
parameters, monitoring of frequency converter running status and fault mes‐
sages) to address the specific requirements of applications.
12.2 Modbus Protocol
12.2.1 Protocol Descriptions
Introduction
Modbus is a master/slave protocol. Only one device may send commands in
the network at a particular time.
The master station manages message exchange by polling the slave sta‐
tions. Unless being approved by the master station, no station may send
message.
In case of a fault during data exchange, if no response is received, the mas‐
ter station will query the slave stations absent from the polling.
If a slave station is not able to understand a message from the master sta‐
tion, it will send an exception response to the master station.
Slave stations can not communicate with each other but through the master’s
software, which reads data from one slave station and sends them to anoth‐
er.
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
response.
● The master station sends a request to all slave stations and does not
wait for their response (broadcasting).
DOK-RCON02-FV*********-IB08-EN-P Bosch Rexroth AG 217/259
Rexroth Frequency Converter Fv
Communication Protocols
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