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MELSEC-Q
5 FUNCTIONS
5.3.2 MODBUS
R
device assignment function
(1) MODBUS
R
device assignment function
(a) The
MODBUS
R
device assignment function automatically converts access
to a slave (QJ71MT91) MODBUS
R
device into access to a programmable
controller CPU device.
(b) Using
MODBUS
R
device assignment parameters, the MODBUS
R
devices
are correlated with the programmable controller CPU device memory.
This allows direct access from the MODBUS
R
/TCP-compatible master
device to the programmable controller CPU device memory.
(c) Since the QJ71MT91 supports large capacities of MODBUS
R
devices, all
the device memories of the programmable controller CPU can be assigned.
Refer to Section 7.4.1 for the MODBUS
R
device sizes.
(2) MODBUS
R
device assignment parameter setting
(a) Set the MODBUS
R
device assignment parameters from the utility package
(GX Configurator-MB).
(Setting from a sequence program is also available. (Refer to Section
9.1.3.))
Refer to Section 7.4 for details of the MODBUS
R
device assignment
parameters.
(b) As the MODBUS
R
device assignment parameters, the default assignment
parameters are available.
Refer to Section 7.4.3 for the default assignment parameters.
Programmable
controller CPU
D300
MODBUS device assignment parameters
MODBUS device
D299
Device memory
400499
D300
400500
D301
400501
Device memory
1234
H
Response message (holding register 400500 = 1234
H
)
Request message (holding register 400500 read request)
QJ71MT91 (Slave function)
Sequence
program
unnecessary
Ethernet
MODBUS /TCP master device
R
R
R