Mitsubishi Electric 800 Series Instruction Manual page 571

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