Precautions - Mitsubishi Electric MELSEC iQ-R Series User Manual

Precautions

The following describes the precautions for changing the operation mode of a redundant system.
Operation mode change in the wait state for the RUN-transition instruction
When the operation mode is changed to the separate mode, the CPU module of the standby system enters the wait state for
the RUN-transition instruction (same as the STOP state). If the operation mode is changed to the backup mode in this state,
the CPU module of the standby system enters the RUN state.
The following describes the precautions for this state.
• If the SP.CONTSW instruction is executed before the CPU module of the standby system enters the RUN state (during
initial processing (when switched to RUN)), an operating status mismatch occurs between two systems and a continuation
error occurs. ( Page 387 System switching during initial processing/initial processing (when switched to RUN))
• If the CPU module of the standby system takes time to change its operating status to the RUN state due to causes such as
access to a file in the CPU module of the standby system, an operating status mismatch occurs between two systems and
a continuation error occurs.
Operation mode change during initial processing (when powered on/switched to RUN)
When the operation mode is changed during initial processing (when powered on or switched to RUN), operation mode
change occurs after the initial processing (when powered on or switched to RUN) is completed. Even if the initial processing
(when powered on or switched to RUN) takes time and a communication error occurs, operation mode change occurs after
the initial processing (when powered on or switched to RUN) is completed.
Consecutive executions of operation mode change
To consecutively execute the operation mode change, certain time intervals between executions are required. If the operation
mode of the redundant system is changed again before the operating status of the CPU module is changed by the previous
operation mode change, an operating status mismatch occurs between two systems and a continuation error may occur.
26 REDUNDANT FUNCTION
26.1 Operation Mode Change
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