Modbus Rtu Communication Specification - Mitsubishi Electric FR-A820-00046 (0.4K) Instruction Manual

5.15.6 MODBUS RTU communication specification

Operation by MODBUS RTU communication or parameter setting is possible by using the MODBUS RTU communication
protocol through the RS-485 terminals of the inverter.
Pr.
331 RS-485 communication
N030 station number
332 RS-485 communication
N031 speed
RS-485 communication stop
N033
bit length
RS-485 communication stop
333
bit length / data length
334 RS-485 communication parity
N034 check selection
343
Communication error count
N080
MODBUS RTU
539
communication check time
N002
interval
549
Protocol selection
N000
NOTE
• To use the MODBUS RTU protocol, set "1" in Pr.549 Protocol selection.
• If MODBUS RTU communication is performed from the master to the address 0 (station number 0), the data is broadcasted,
and the inverter does not send any reply to the master. To obtain replies from the inverter, set Pr.331 RS-485 communication
station number ≠ "0 (initial value)".
• Some functions are disabled in broadcast communication. (Refer to
• If a communication option is installed with Pr.550 NET mode operation command source selection = "9999 (initial value)",
commands (operation commands) transmitted via RS-485 terminals become invalid. (Refer to
652
5. PARAMETERS
5.15 (N) Communication operation parameters
Initial
Name
value
0
96
1
1
2
0
9999
0
Setting
range
0 Broadcast communication
Specify the inverter station number.
1 to 247 Enter the inverter station numbers when two or more inverters are
connected to one personal computer.
3, 6, 12, 24,
Select the communication speed.
48, 96, 192,
The setting value × 100 equals the communication speed.
384, 576,
For example, enter 96 to set the communication speed of 9600 bps.
768, 1152
0 Stop bit length 1 bit
1 Stop bit length 2 bits
0 Stop bit length 1 bit
1 Stop bit length 2 bits
10 Stop bit length 1 bit
11 Stop bit length 2 bits
Without parity check
0
Stop bit length 1 bit / 2 bits (depends on the setting of Pr.333)
With parity check at odd numbers
1
Stop bit length 1 bit
With parity check at even numbers
2
Stop bit length 1 bit
Displays the communication error count during MODBUS RTU
—
communication. Read-only.
MODBUS RTU communication is available, but the inverter output is
0
shut off in the NET operation mode.
Set the interval of the communication check (signal loss detection)
0.1 to 999.8 s
time (same specifications as Pr.122).
9999 No communication check (signal loss detection)
0 Mitsubishi inverter protocol (computer link)
1 MODBUS RTU protocol
page
Description
Valid when Pr.N034 (Pr.334) =
"0"
Valid when Pr.334 = "0"
655.)
page 380.)