Mitsubishi QJ71MB91, User Manual

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5
FUNCTIONS
5.3 Slave Function
5.3.2 MODBUS(R) device assignment function
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5.3.2 MODBUS(R) device assignment function
The MODBUS device assignment function automatically converts access to a slave
(QJ71MB91) MODBUS device into access to a programmable controller CPU device.
This allows direct access from the MODBUS compatible master device to the
programmable controller CPU device memory.
Supporting the MODBUS devices of large capacity, the QJ71MB91 allows all device
memories of the programmable controller CPU to be assigned.(
Section 7.3.1)
(1) MODBUS device assignment parameter setting
Set the MODBUS device assignment parameters to the slave (QJ71MB91).
The following settings are possible for the MODBUS device assignment
parameters.
(a) Correlating the MODBUS device to the programmable controller CPU device
memory.
When a message requesting an action such as write coil is received from the
master, the access to the MODBUS device is automatically converted into
access to the programmable controller CPU device.(
Section 7.3.1 to Section
7.3.3)
Figure 5.13 MODBUS device and programmable controller CPU device
D300
R
R
D299 400499
D300 400500
D301 400501
Device
Programmable
controller CPU
No sequence
program required
QJ71MB91 (Slave function)
MODBUS device assignment parameter
Device memory
MODBUS device
Request message (Write 1234
H
to holding
register 400500)
MODBUS
Master
device
RS-232, RS-422 or RS-485
1234
H
R