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MELSEC-Q
5 FUNCTIONS
5.3 Slave Function
This section explains the functions of the QJ71MT91 as a slave of MODBUS
R
/TCP.
5.3.1 Automatic response function
The automatic response function allows the QJ71MT91 (slave function) to
automatically execute the processing requested by the function code of a request
message from the master and return a response message to the master.
The automatic response function uses the MODBUS
R
device assignment function.
Refer to Section 5.3.2 for the MODBUS
R
device assignment function.
Refer to Section 4.1 for the function codes supported by the slave function of the
QJ71MT91.
Request message (function code)
Ethernet
MODBUS /TCP master device
R
Response message
Sequence
program
unnecessary
Programmable
controller CPU
Device memory
QJ71MT91
(Slave function)
1)
Identification of
function code
2)
Execution of
corresponding
processing
3)
Sending of
response
message
4)
Receipt of
request message
