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Ras Functions; Output Reset Function For Communication Errors; Automatic Return Function - Mitsubishi Electric QJ71LP21 Reference Manual

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3 SPECIFICATIONS

3.2.2 RAS functions

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RAS stands for "Reliability", "Availability" and "Serviceability" and is an automated
facility for overall ease of use.

(1) Output reset function for communication errors

Remote I/O net will set all output of remote I/O stations to off when there is a data
link error.
It will also set all output of remote I/O stations to off when the data links are
operating properly but the remote master station CPU module is down.
If you wish to save the output of the remote I/O station when there is an error,
use the detailed I/O allocation settings in the PLC parameters for the remote I/O
station to set the "Error time output mode" settings to "Hold".
Refer to the GX Developer Operating Manual for more information about setting
the PLC parameters.
If the remote master station has a remote I/O station that has experienced a data
link communication error or communication stop, it saves the received data
(X,B,W) from the remote I/O station in the immediately preceding data.

(2) Automatic return function

By using this function, when a station that has been disconnected from the data
link due to a data link error returns to the normal status, it automatically returns to
the system to resume the data link.
When the data link of a remote I/O station is resumed (the "D.LINK" LED is on),
the remote I/O station resets all the mounted modules. If data link is resumed by
connecting/disconnecting the link cable, the module is not reset. When the
parameters of a remote I/O station are changed, then those of the remote master
station are changed, the remote master station is reset or the remote I/O station
is reset (powered off and then on, or reset switch is turned on), the modules will
be reset when the remote I/O station returns to the system to resume the data
link. Consequently, even if the output setting under a CPU error is set to HOLD
(retention) in an output module, digital-analog conversion module, and
temperature adjustment module, output cannot be retained when data link is
resumed.
1) The remote I/O station No. 2 is disconnected
due to a data link error.
Remote
Remote I/O
master
station
station
(station
(station
No. 1)
No. 0)
Network No. 1
Remote I/O
Remote I/O
station
station
(station
(station
No. 5)
No. 4)
POINT
There is a limit to the number of faulty stations that can return to the system within
one link scan. For details, see Section 5.1.4, "Supplemental Settings."
Down
Remote I/O
station
(station
No. 2)
Return
Remote I/O
station
(station
No. 3)
MELSEC-Q
2) The station No. 2 recovers to the normal
status and returns to the system.
Remote
Remote I/O
master
station
station
(station
(station
No. 1)
No. 0)
Network No. 1
Remote I/O
Remote I/O
station
station
(station
(station
No. 5)
No. 4)
Return
Remote I/O
station
(station
No. 2)
Remote I/O
station
(station
No. 3)
3 - 14

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