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MELSEC-Q
7 PARAMETER SETTING
7.2.4 MODBUS
®
/TCP setting
(1) Local slave station port No.
Set the port No. on the QJ71MT91 side for receiving a request message from the
master using the slave function of the QJ71MT91.
POINT
(1) The specifications of the MODBUS
R
/TCP protocol define that "502" should be
used as the port No. for the slave.
In this setting, the default value is "502" and normally need not be changed.
(2) When specifying a value of 32768 (8000
H
) or more in a sequence program, set
the value in hexadecimal.
(2) Target slave port No. for automatic communication function
Set the target slave port No. for issuing a request message using the automatic
communication function (master function) of the QJ71MT91.
POINT
(1) The specifications of the MODBUS
R
/TCP protocol define that "502" should be
used as the port No. for the slave.
In this setting, the default value is "502" and normally need not be changed.
(2) When specifying a value of 32768 (8000
H
) or more in a sequence program, set
the value in hexadecimal.
(3) CPU response monitoring timer value
(a) When the QJ71MT91 receives a request message from the master and the
programmable controller CPU starts its processing, the QJ71MT91 waits
for the response from the programmable controller CPU. The time allowed
for the QJ71MT91 to wait is set by the CPU response monitoring timer
value.
This timer allows the QJ71MT91 to cancel the wait status on the master
side when a response to the master is not available due to an error
occurred in the programmable controller CPU.
1)
2)
3)
Master device
QJ71MT91
CPU response
monitoring timer
Programmable
controller CPU
Request
Normal response
Request
Exception response
Start
Reset
Start
Timeout
Processing
Error occurred