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6.2 Redundant System Network Overview
6.2.2 MELSECNET/H Remote I/O network
6
(b) Operation when error occurs in remote I/O station
* 4 : Set the output mode for error occurrence in the I/O assignment detailed setting of the PLC param-
eter dialog box.
Refer to the following manual for details of the I/O assignment detailed setting.
QCPU User's Manual (Function Explanation/Program Fundamentals)
(10)Precautions for Using Redundant System in MELSECNET/H Remote I/O
Network
(a) Programming of MELSECNET/H
The MELSECNET/H network detects a temporary communication error
depending on conditions such as power supply ON/OFF or cable and noise.
Create the program using the MELSECNET/H so that it will not stop controlling
even when the temporary communication error is detected.
(b) Error detection by turning ON/OFF other station (including standby system)
When turning ON/OFF power supply of the other station (including standby
system) CPU module or booting and shutting down the personal computer where
the MELSECNET/H board is mounted, the MELSECNET/H module of the control
system may issue a system switching request, detecting a temporary
communication error.
When the above-mentioned system switching request is issued before the
standby system is started up, a continuation error "CAN'T SWITCH" may be
detected in the control system CPU module. In this case, control can be continued
normally. Therefore, create the program so that control will not be stopped due to
error detection.
For canceling the error "CAN'T SWITCH", refer to Section 8.1.16.
For details of the MELSECNET/H network system, refer to the following manual.
Q Corresponding MELSECNET/H Network System Reference Manual
(PLC to PLC network)
Table6.4 Operation When Error Occurs in remote I/O station
Settings of operation mode for
error occurrence
Redundant CPU
control status
Data link operation of
MELSECNET/H remote I/O
network
Output operation from remote
I/O station
Redundant
CPU
Remote I/O
station
Stop
Stop
Stops control.
(Stop error)
All stations stop data link.
Depends on the output mode
hold/clear settings for error
occurrence.
*4
Continue
Continue
Stop
Continues control.
(Continue error)
The faulty station is disconnected
from the system.
The other stations continue
normal data link.
The output of the faulty station
follows the hold/clear setting in
the error-time output mode.
*4
All stations output normally.
Continue
All stations continue data link.
All stations output normally.
