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Processing details
• Switches between the control system and standby system at the END processing of the scan executed with the
SP.CONTSW instruction.
• When using the SP.CONTSW instruction for system switching, the "manual switching enable flag (SM1592)" must have
been turned ON (enabled) in advance.
• (S) is provided to identify the processing block of the program where system switching occurred when multiple
SP.CONTSW instructions are used.
• At (S), specify a value within the ranges -32768 to -1 and 1 to 32767 (1H to FFFFH).
• The (S) value specified by the SP.CONTSW instruction is stored into the "system switching instruction argument (SD6)" of
the error common information when the system switching is normally completed.
instructions are executed during the same scan, the argument of the SP.CONTSW instruction executed first is stored into
the system switching instruction argument (SD6).
*2 The (S) value specified for the SP.CONTSW instruction can be confirmed in the error common information of the PLC diagnostics dialog
box on GX Developer.
• The (S) value specified by the SP.CONTSW instruction is stored into the "system switching instruction argument (SD1602)"
of the new control system CPU module when system switching is normally completed.
the new control system CPU module, which the SP.CONTSW instruction was used for system switching can be confirmed.
*3 The new control system CPU module means the CPU module that was switched from the standby system to the control system by the
SP.CONTSW instruction.
• The error completion device is turned ON by the control system CPU module when system switching by the SP.CONTSW
instruction was unsuccessful. When OPERATION ERROR is detected due to any of the following reasons at the execution
of the SP.CONTSW instruction, the error completion device is turned ON during the instruction execution.
• 0 is specified at (S) of the executed SP.CONTSW instruction.
• The "manual switching enable flag (SM1592)" is OFF.
• The SP.CONTSW instruction was executed by the standby system in the separate mode.
• The SP.CONTSW instruction was executed in the debug mode.
If systems could not be switched due to any of the reasons given in the following table, the error completion device turns ON
when system switching is executed in the END processing.
Reason No.
0
1
2
3
4
5
6
7
8
9
10
When the error completion device was turned ON due to unsuccessful system switching, 16 is stored into the "reason(s) for
system switching (SD1588)" and the reason No. of the above table into the "reason(s) for system switching failure (SD1589)".
• Use a user program or GX Developer to turn OFF the error completion bit that has turned ON. If normal system switching is
performed by the execution of the SP.CONTSW instruction with the error completion device ON, the error completion
device of the new standby system CPU module is also turned OFF. When system switching is performed due to a factor
other than the SP.CONTSW instruction, however, the error completion device is not turned OFF.
Reasons for system switching failure
Normally completed
Tracking cable is disconnected or faulty.
Hardware fault, power-off, reset or watchdog timer error occurred in the standby system.
Watchdog timer error occurred in the control system.
Preparations being made for tracking transfer.
Communication time-out.
Stop error occurred in the standby system. (Excluding watchdog timer error)
Operating status different between the control system and standby system.
Memory copy being executed from the control system to the standby system.
Write during RUN being executed.
Network fault detected by the standby system.
11 REDUNDANT SYSTEM INSTRUCTIONS (FOR REDUNDANT CPU)
*2
When multiple SP.CONTSW
*3
By reading the SD1602 value from
11.1 System Switching
11
881
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