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(7) Checking with special relays and special registers
The status of execution of latch data backup to the standard ROM or restoration operation can be checked by
SM671, SM676, SD671 to SD679.
(8) Precautions
The following provides precautions for backing up latch data.
1) Do not power off or reset the CPU module during backup of latch data. If performed, "RESTORE ERROR"
(error code: 2221) is detected, and backup data is not restored (The backup data are deleted).
2) Even if the backup data exists, the initial device value has a priority over the backup data when the initial
device value is set.
Therefore, the device where the initial device value setting is configured is overwritten by the device data
of the initial device value after reflecting the backup data.
3) Even if the latch device or latch range setting is used, backup data has a priority. Therefore, even when data
of latch device and latch range setting are changed after backup, it is overwritten by data backed up when
the CPU module is powered off and then on or is reset.
4) Devices where local device range setting is configured are not backed up. They are initialized (cleared to 0)
when the CPU module is powered off and then on or is reset.
5) When the number of writes to the standard ROM exceeds 100,000 times ("FLASH ROM ERROR" (error
code: 1610) is detected), data may not be normally backed up.
6) Backup data cannot be deleted unless the data are deleted or the storage location memory (standard ROM)
for the backup data is formatted.
7) The following operations cannot be performed during latch data backup. Perform them after the backup
operation.
If performed, an error is displayed on the GX Developer screen.
• Format PLC memory (standard ROM only)
• Latch data backup by remote operation
• Online change (ladder mode, files, function block)
• Write the program memory to ROM
• Write to PLC (Flash ROM)
CHAPTER6 FUNCTIONS
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