Mitsubishi Electric FR-F800 Series Instruction Manual page 522

 Communication specifications
• The communication specifications are shown in the following table.
Communication protocol
Conforming standard
Number of connectable units
Communication speed
Control procedure
Communication method
Communication
specifications
Time delay 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 (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
Monitoring, operation command,
frequency setting (RAM)
Parameter read/write, frequency setting
(EEPROM)
Parameter clear / All parameter clear
Reset command
• Query
A message is sent to the slave (the inverter) having the address specified by the master.
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Item
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 method
Half-duplex system
Character
Binary (fixed at 8 bits)
system
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.
Parity check
Even parity check, stop bit length 1 bit.
Error check CRC code check
Terminator Not available
Not available
Query communication
Programmable controller
(Master)
Inverter (slave)
Broadcast communication
Programmable controller
(Master)
Inverter (slave)
Item
Less than 12 ms
Less than 30 ms
< 5 s
No reply
search engine
Description
Inverter response time
(Refer to the following table for the
data check time)
Query Message
Response Message
Data absence time
(3.5 bytes or more)
Query Message
Check time
No Response
5.12 (N) Communication operation parameters
1
Related parameter
Pr.549
2
—
Pr.331
Pr.332
3
—
—
—
4
—
Pr.333
5
Pr.334
—
—
6
—
7
8
9
10
521
5. PARAMETERS