Modbus® Rtu Communication Specification - Mitsubishi Electric FR-A820-00046 Instruction Manual

Parameters
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.
331
N030
332
N031
N033
333
334
N034
343
N080
539
N002
549
N000
NOTES 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 5-658.)
If a communication option is mounted with Pr. 550 "NET mode operation command source selec-
tion" = "9999 (initial value)", commands (operation commands) transmitted via RS-485 terminals
become invalid. (Refer to page 5-282.)
Upon delivery the FR-A800-E inverter models are not equipped with the RS-485 terminal block.
FR-A800
Name
RS-485 communication
station number
RS-485 communication
speed
RS-485 communication
stop bit length
RS-485 communication
stop bit length / data
length
RS-485 communication
parity check selection
Communication error
count
Modbus® RTU
communication check
time interval
Protocol selection
(N) Operation via communication and its settings
Initial Setting
Description
value range
0 Broadcast communication
0
Inverter station number specification
1 to 247
Set the inverter station numbers when two or more
inverters are connected to one personal computer.
Set the communication speed.
3, 6, 12, 24,
The setting value × 100 equals the communication
48, 96, 192,
96 speed.
384, 576,
For example, if 96 is set, the communication speed is
768, 1152
9600 bps.
0 Stop bit length 1 bit
1
1 Stop bit length 2 bits
0 Stop bit length 1 bit
1 Stop bit length 2 bits
1
10 Stop bit length 1 bit
11 Stop bit length 2 bits
Without parity check
0
The stop bit length is selectable between 1 bit and 2
bits (according to Pr. 333).
With parity check at odd numbers
2
1
Stop bit length 1 bit
With parity check at even numbers
2
Stop bit length 1 bit
Displays the communication error count during
⎯
0
Modbus® RTU communication. Read-only.
Modbus® RTU communication, but the inverter trips in
0
the NET operation mode.
Set the interval of the communication check (signal
9999
0.1 to 999.8 s
loss detection) time. (same specifications as Pr. 122)
9999 No communication check (signal loss detection)
0 Mitsubishi inverter protocol (computer link)
0
1 Modbus® RTU protocol
Valid when
Pr. 343 (P.N034) = 0
Valid when
Pr. 343 (P.N034) = 0
5 - 655