Modbus Rtu Communication Specification - Mitsubishi Electric 800 Series 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 from the RS-485 terminals of the inverter.
Pr. Name
331 RS-485 communication
N030 station number
332 RS-485 communication
N031 speed
RS-485 communication
N033
stop bit length
RS-485 communication
333 stop bit length / data
length
334 RS-485 communication
N034 parity check selection
343 Communication error
N080 count
MODBUS RTU
539
communication check
N002
time interval
549
Protocol selection
N000
NOTE
• To use the MODBUS RTU protocol, set "1" to 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
page 571.)
• If a communication option is mounted with Pr.550 NET mode operation command source selection = "9999 (initial value)",
commands (operation commands) transmitted via RS-485 terminals become invalid. (Refer to
(N) Operation via communication and its settings
Initial Setting
value range
0
0
1 to 247
3, 6, 12, 24,
48, 96, 192,
96
384, 576, 768,
1152
0
1
1
0
1
1
10
11
0
2
1
2
0 ―
0
9999
0.1 to 999.8 s
9999
0
0
1
Description
Broadcast communication
Inverter station number specification
Set the inverter station numbers when two or more
inverters are connected to one personal computer.
Set the communication speed.
The setting value  100 equals the communication speed.
For example, if 96 is set, the communication speed is
9600 bps.
Stop bit length 1 bit
Valid when Pr.N034 (Pr.334)
= "0"
Stop bit length 2 bits
Stop bit length 1 bit
Stop bit length 2 bits
Valid when Pr.334 = "0"
Stop bit length 1 bit
Stop bit length 2 bits
Without parity check
Stop bit length 1 bit / 2 bits (depends on the setting of
Pr.333)
With parity check at odd numbers
Stop bit length 1 bit
With parity check at even numbers
Stop bit length 1 bit
Displays the communication error count during MODBUS
RTU communication. Read-only.
MODBUS RTU communication, but the inverter trips in the
NET operation mode.
Set the interval of the communication check (signal loss
detection) time (same specifications as Pr.122).
No communication check (signal loss detection)
Mitsubishi inverter protocol (computer link)
MODBUS RTU protocol
page
PARAMETERS
301.)
5
GROUP
N
569