Communication Specifications; Message Format - Mitsubishi Electric FR-A820-00046 (0.4K) Instruction Manual

 Communication specifications
• The communication specifications are given below.
Item
Communication protocol
Conforming standard
Number of 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 (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
Programmable controller
(Master)
Broadcast communication
Programmable controller
(Master)
• Data check time
Item
Monitoring, operation command,
frequency setting (RAM)
Parameter read/write,
frequency setting (EEPROM)
Parameter clear / all clear
Reset command
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
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 available
Not available
Query Message
Inverter (slave)
Data absence time
(3.5 bytes or more)
Query Message
Inverter (slave)
Check time
< 12 ms
< 30 ms
< 5 s
No reply
Description
Inverter response time
(Refer to the following table for the
data check time)
Response Message
No Response
5.15 (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
653
5. PARAMETERS