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Communication operation and setting
4
PARAMETERS
(1) Communication specification
The communication specifications are given below.
(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.
Item Description
Related
Parameter
Communication protocol Modbus-RTU protocol Pr. 549
Conforming standard EIA-485(RS-485) —
Number of connectable devices 1:N (maximum 32 units), setting is 0 to 247 stations Pr. 117
Communication speed Selected among 4800/9600/19200 and 38400bps Pr. 118
Control procedure Asynchronous —
Communication method Half-duplex —
Communication
Character system Binary (always 8 bits) —
Start bit 1bit —
Stop bit length
Select from the following three types
No parity, stop bit length 2 bits
No odd parity, stop bit length 1 bits
Even parity, stop bit length 1 bit
Pr. 120
Parity check
Error check CRC code check —
Terminator Not used —
Waiting time setting Not used —
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.