472
28 FUNCTIONS
28.4 Memory Copy from Control System to Standby System
Memory copy with the special relay and special register
The following describes the execution procedure of memory copy using the special relay and special register.
Special relay to be used
The following table lists the special relay areas used in memory copy.
For details on the special relay (SM), refer to the following.
Page 803 List of Special Relay Areas
Special register to be used
The following table lists the special register used in memory copy.
*1 Even after the CPU module is turned off and on or reset, the result of the memory copy executed just before this reset operation can be
checked since this register area is a latch area.
For details on the special register (SD), refer to the following.
Page 833 List of Special Register Areas
Execution procedure
To execute the memory copy with the special relay and special register, use the special relay and special register of the
standby system CPU module.
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 memory copy
is completed.
• When SM1655 is on, the memory copy with the special relay and special register cannot be started. Execute the memory
copy again after turning off SM1655.
2. Store 03D1H (Standby system CPU module) 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 LEDs
of the redundant function modules in both systems flash (at 200ms intervals).
4. When the memory copy is completed, the MEMORY COPY LED of the control system turns off and that of the standby
system turns on.
5. Turn off and on or reset the standby system CPU module. The MEMORY COPY LED of the standby system turns off.
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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