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MELSEC-Q
5 DATA COMMUNICATION USING THE MELSEC COMMUNICATION
PROTOCOL
5.1.5 Support for the QCPU remote password function
This section explains an overview of the remote password function when a remote
password is set for the Q series C24 mounted to a QCPU.
See Chapter 3 of the User's Manual (Application) for a detailed explanation.
(1) Checking remote passwords
If the following items are set to the QCPU using GX Developer, the Q series C24
performs a remote password check whenever an external device accesses the
PLC using the modem function of the Q series C24.
(a) Setting by GX Developer
• When the remote password is set on the QCPU with the Q series C24.
• When the Q series C24 is set to be subject to the remote password check.
(b) Access in which the remote password is checked
The remote password is checked when the following access is attempted.
Access attempts to all PLCs of the local station (the local station with the Q
series C24 and other stations accessed via the local station) are subject to
the remote password checking.
(Access function to the PLC in which the remote password is checked)
• Data communication using the MC protocol
• Access to the PLC using GX Developer
The remote password is not checked in data communication using the
non procedure/bidirectional protocols.
(c) Remote password to be checked
The check is performed against the remote password set to the local
station QCPU with the Q series C24.
Access to the specified station is allowed if the remote password
specified by the user and the remote password set to the QCPU match
when accessing.
(2) Data communication procedure
1) Initialize the modem.
2) Connect the line from the external device.
3) Unlock (cancel) the remote password of the QCPU belonging to the station
with the Q series C24 mounted from the external device via the dedicated
command for communication using the MC protocol.
4) Initiate the data communication between the external device and PLC using
the MC protocol.
5) Disconnect the modem line from the external device side when completing
the data communication using the MC protocol.
The remote password is automatically locked when the modem is
disconnected.