Mitsubishi Electric FR-A800, Instruction Manual

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Parameters (N) Operation via communication and its settings
FR-A800 5 - 631
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.
Message format
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
⎯
Communica-
tion specifica-
tions
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 2 bits
Odd parity check, stop bit length 1 bit
Even parity check, stop bit length 1 bit
Pr. 334
Parity check
Error check CRC code check
⎯
Terminator Not used
⎯
Waiting time setting Not used
⎯
Tab. 5-279: Communication specifications
NOTE There are two serial transmission modes, the ASCII (American Standard Code for Information Inter-
change) 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.
I001227E
Fig. 5-316: Message format
Query communication
Query Message
Response Message
Programmable controller
(Master)
Inverter (slave)
Data absence time
(3.5 bytes or more)
Inverter response time
(Refer to the following table for the data
check time)
Broadcast communication
Query Message
No Response
Inverter (slave)
Programmable controller
(Master)