Mitsubishi Electric 800 Series, Instruction Manual, Page: 571 / 727

(N) Operation via communication and its settings
570
PARAMETERS
 Communication specifications
• The communication specifications are given below.

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.
 Message format
• Data check time
• Query
A message is sent to the slave (for instance, the inverter) having the address specified by the master.
Item Description
Related
parameter
Communication protocol MODBUS RTU protocol Pr.549
Conforming standard EIA-485 (RS-485) ―
Connectable units 1:N (maximum 32 units), setting is 0 to 247 stations Pr.331
Communication Speed
Selected among 300/600/1200/2400/4800/9600/19200/38400/57600/76800/
115200 bps
Pr.332
Control procedure Asynchronous system ―
Communication method Half-duplex system ―
Communication
specifications
Character system Binary (fixed at 8 bits) ―
Start bit 1 bit ―
Stop bit length
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
Pr.333
Pr.334
Parity check
Error check CRC code check ―
Terminator Not used ―
Waiting time setting Not used ―
Item Check time
Various monitors, operation command,
Frequency setting (RAM)
<12 ms
Parameter read/write,
frequency setting (EEPROM)
<30 ms
Parameter clear / all clear <5 s
Reset command No answer
Query communication
Broadcast communication
Query Message
Query Message
Response Message
Inverter (slave)
Inverter (slave)
Programmable controller
(Master)
Programmable controller
(Master)
No Response
Inverter response time
(Refer to the following table for the
data check time)
Data absence time
(3.5 bytes or more)