Table of Contents
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(1)
Communication specification
The communication specifications are given below.
Item
Communication protocol
Conforming standard
Number of connectable devices
Communication speed
Control procedure
Communication method
Character system
Start bit
Stop bit length
Communication
Parity check
Error check
Terminator
Waiting time setting
(2)
Outline
The Modbus protocol is the communication protocol developed by Modicon for PLC.
The Modbus protocol performs serial communication between the master and slave using the dedicated message frame.
The dedicated message frame has the functions that can perform data read and write. Using the functions, you can read
and write the parameter values from the inverter, write the input command of the inverter, and check the operating status. In
this product, the inverter data are classified in the holding register area (register addresses 40001 to 49999). By accessing
the assigned holding register address, the master can communicate with the inverter which is a slave.
REMARKS
There are two different serial transmission modes: ASCII (American Standard Code for Information Interchange) mode and RTU
(Remote Terminal Unit) mode. This product supports only the RTU mode in which 1-byte (8-bit) data is transmitted as it is.
Only the communication protocol is defined by the Modbus protocol, and the physical layer is not stipulated.
Communication operation and setting
Description
Modbus-RTU protocol
EIA-485(RS-485)
1:N (maximum 32 units), setting is 0 to 247 stations
Selected among 4800/9600/19200 and 38400bps
Asynchronous
Half-duplex
Binary (always 8 bits)
1 bit
Select from the following three types
No parity, stop bit length 2 bits
No odd parity, stop bit length 1 bit
Even parity, stop bit length 1 bit
CRC code check
Not used
Not used
Related
Parameter
Pr. 549
—
Pr. 117
Pr. 118
—
—
—
—
Pr. 120
—
—
—
4
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