618
37 FUNCTIONS
37.1 System Switching
■Special relay
The following table shows the special relay for system switching and the storage status of the CPU modules in the control
system and standby system.
: Stored, : Not stored
■Special register
The following table shows the special register for system switching and the storage status of the CPU modules in the control
system and standby system.
: Stored, : Not stored
*1 When the system switching has not been normally completed, a value is stored in this special register area of the control system.
CTRL LED and SBY LED of the redundant function module
System switching results can be checked with the CTRL LED and SBY LED on the front of the redundant function module.
SM
number
Name Storage status at system switching
New control system
CPU module
New standby system
CPU module
SM1637 System switching detection (standby system to control system)
SM1643 ON for only one scan after system switching (standby system to control system)
SM1644 ON for only one scan after system switching (control system to standby system)
SM1645 System switching request from a network module
SM1646 System switching by a user
SD
number
Name Storage status at system switching
New control system
CPU module
New standby system
CPU module
SD1642 BACKUP/SEPARATE LED flashing cause
SD1643 System switching cause
SD1644 Cause of system switching failure
*1
SD1645 System switching request status from a network module of own system
SD1646 System switching request status from a network module of the other system
SD1648 Cause of the other system monitoring error
SD1649 System switching cause (when the systems are successfully switched)
SD1650 System switching instruction ID number
Switching from the standby system to the control system Switching from the control system to the standby system
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