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MELSEC-Q
5 FUNCTIONS
5 FUNCTIONS
This chapter explains the functions of the QJ71MT91.
5.1 Function List
The function list of the QJ71MT91 is indicated below.
Function Description
Reference
Automatic communication
Automatically issues device read/write request
messages from the master (QJ71MT91) to the
MODBUS
R
/TCP-compatible slave device.
Section
5.2.1
Master function
Dedicated instruction ( 1)
Allows reading/writing of the MODBUS
R
device at any
timing with a sequence program.
Chapter 10
Automatic response
function( 2)
Automatically performs the processing corresponding to
the function code in the request message received from
the master, and automatically sends a response
message.
Section
5.3.1
Slave function
MODBUS device
assignment function( 3)
Automatically converts access from the slave
(QJ71MT91) to the MODBUS
R
device into access to
the programmable controller CPU device. Users can
assign it as desired.
This enables direct access from the MODBUS
R
/TCP-
compatible master device to the programmable
controller CPU device memory.
Section
5.3.2
KeepAlive function
Confirms the status of communication with the target
device where a TCP connection has been established.
When communication is not made for a given period of
time between the QJ71MT91 and the open target
device, the QJ71MT91 checks the target device for
existence and cuts off unnecessary TCP connections.
Section 5.4
Router relay function
Exchanges data with the device connected to other
Ethernet via router(s) and/or gateway(s).
(This is not a function with which the QJ71MT91
operates as a router.)
Section 5.5
Ethernet function
IEEE802.3 frame
Allows connection with the device that uses the
IEEE802.3 frame.
Section 6.6
1: Dedicated instructions are not available when the QJ71MT91 is installed to a
MELSECNET/H remote I/O station or a redundant system.
2: When the QJ71MT91 is mounted on a MELSECNET/H remote I/O station,
there is a restriction on the function code supported by the automatic
response function.
Refer to Section 4.1 for details.
3: When the QJ71MT91 is mounted on a MELSECNET/H remote I/O station,
there is a restriction on the assignment range of the MODBUS
R
device
assignment function.
Refer to Section 7.4.2 for details.
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