26 REDUNDANT FUNCTION
26.4 Memory Copy from Control System to Standby System
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Memory copy using the special relay and special register
The execution procedure for the memory copy using the special relay and special register is described below.
Special relay to be used
The memory copy function uses the following special relay areas.
For details on the special relay (SM), refer to the following.
Page 645 List of Special Relay Areas
Special register to be used
The memory copy function uses the following special register areas.
*1 This is a latch area. Even when the system is powered off and on or reset, the result of the memory copy executed immediately before
power-on or reset can be checked.
For details on the special register (SD), refer to the following.
Page 668 List of Special Register Areas
Execution procedure
To execute the memory copy using the special relay and special register, use the special relay and special register of the CPU
module in the control system.
1. Check that SM1654 (Memory copy being executed) and SM1655 (Memory copy completion) are off.
• When SM1654 is on, the memory copy is being executed. Another memory copy cannot be started until the current
memory copy is completed.
• When SM1655 is on, the memory copy using the special relay and special register cannot be started. Turn off SM1655, and
execute the memory copy.
2. Store 03D1H (CPU module of the standby system) in SD1653 (Memory copy destination I/O number).
3. Turn on SM1653 (Memory copy start) to execute the memory copy. During the memory copy, the MEMORY COPY LED
of the redundant function module flashes (in 200ms intervals) in both systems.
4. When the memory copy is completed, the MEMORY COPY LED turns off in the control system and turns on in the
standby system.
5. Power off and on or reset the standby system. The MEMORY COPY LED turns off in the standby system.
SM number Name
SM1653 Memory copy start
SM1654 Memory copy being executed
SM1655 Memory copy completion
SM1656 Auto memory copy
SD number Name
SD988
*1
Memory copy completion status (latch)
SD1653 Memory copy destination I/O number
SD1654 Memory copy completion status
Control system Standby system
Control system Standby system
Control system Standby system
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