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Communication operation and setting
4
PARAMETERS
(1) Communication
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 drive unit, write the input command of the drive unit, and check the operating
status. In this product, the drive unit 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 drive unit 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 4800/9600/19200/38400bps Pr.118
Control procedure
Asynchronous
Communication method
Half-duplex
Communication
Character
system
Binary (always 8 bits)
Start bit
1 bit
Stop bit length
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
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-is.
Only the communication protocol is defined by the Modbus protocol, and the physical layer is not stipulated.