• The communication specifications are shown in the following table.
Number of connectable units
Stop bit length
Time delay setting
• The MODBUS communication protocol was developed by Modicon for programmable controllers.
• The MODBUS protocol uses exclusive message frames to perform serial communication between a master and slaves.
These exclusive message frames are provided with a feature called "functions" that allows data to be read or written. These
functions can be used to read or write parameters from the inverter, write input commands to the inverter or check the
inverter's operating status, for example. This product classifies the data of each inverter into holding register area (register
address 40001 to 49999). The master can communicate with inverters (slaves) by accessing pre-assigned holding register
• There are two serial transmission modes, the ASCII (American Standard Code for Information Interchange) mode and the RTU
(Remote Terminal Unit) mode. However, this product supports only the RTU mode, which transfers 1 byte data (8 bits) as it
is. Also, only communication protocol is defined by the MODBUS protocol. Physical layers are not stipulated.
• Data check time
Monitoring, operation command,
frequency setting (RAM)
Parameter read/write, frequency setting
Parameter clear / All parameter clear
A message is sent to the slave (the inverter) having the address specified by the master.
MODBUS RTU protocol
1: N (maximum 32 units), setting is 0 to 247 stations
Selected among 300/600/1200/2400/4800/9600/19200/38400/57600/76800/
Binary (fixed at 8 bits)
Select from the following three types:
No parity check, stop bit length 1 bit / 2 bits (depends on the setting of Pr.333).
Odd parity check, stop bit length 1 bit.
Even parity check, stop bit length 1 bit.
CRC code check
Data absence time
(3.5 bytes or more)
Less than 12 ms
Less than 30 ms
< 5 s
Inverter response time
(Refer to the following table for the
data check time)
5.12 (N) Communication operation parameters