Outline; Message Format - Mitsubishi Electric 800 Series Instruction Manual

4.5.2

Outline

• 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 (for instance,. slaves) by accessing pre-assigned
holding register addresses.
NOTE
• 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.
4.5.3

Message format

62
PARAMETER
Query communication
Query Message
Programmable controller
(Master)
Inverter (slave)
Broadcast communication
Query Message
Programmable controller
(Master)
Inverter (slave)
Inverter response time
(Refer to the following table for the
data check time)
Response Message
Data absence time
(3.5 bytes or more)
No Response