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33 Applied Instructions (Extension File Register Control)
33.5 RWER / Rewrite to ER
768
FXCPU Structured Programming Manual
[Basic & Applied Instruction]
2. Cautions on writing data to the memory cassette (EEPROM) for the FX3G PLCs
Memory cassettes adopt EEPROM. Note the following contents when writing data to extension file registers
in a memory cassette with the RWER instruction.
• Do not turn OFF the power while this instruction is being executed. If the power is turned OFF, execution of
this instruction may be aborted. If execution is aborted, the data may be lost.
Be sure to back up the data before executing this instruction.
3. About the allowable number of times of writing operations in memory
Note the following when accessing the extension file registers:
• For the FX
3U and FX3UC PLCs
The memory cassette (flash memory) allows up to 10,000 times of writing operations.
The number of times of writing operations counts up each time the INITR, RWER or INITER instruction is
executed. Do not let the number of times of writing operations exceed the allowable number of times of
writing operations. When a continuous operation type instruction is executed, writing operation to the
memory occurs for each operation cycle of the PLC. To avoid this, be sure to use pulse operation type
instructions.
The number of times of writing operations does not count up when the LOADR, SAVER or LOGR
instruction is executed. However, the SAVER and LOGR instructions require the target write sectors to be
initialized before executing the instructions. Note that, when initializing by using the INITR or INITER
instruction, the number of times of writing operations in the memory counts up every time the NITR or
INITER instruction is executed.
• For the FX
3G and FX3GC PLCs
The memory cassette (EEPROM) and PLC's built-in memory (EEPROM) allow up to 10,000 times and
20,000 times of writing operations, respectively. The number of times of writing operations counts up each
time the RWER instruction is executed. Do not let the number of times of writing operations exceed the
allowable number of times of writing operations.
When a continuous operation type instruction is executed, writing operation to the memory occurs for each
operation cycle of the PLC.
To avoid this, be sure to use pulse operation type instructions.
The number of times of writing operations does not count up when the LOADR instruction is executed.
Error
An operation error is caused in the following cases. The error flag M8067 turns ON, and the error code is
stored in D8067.
1) When the last device number to be transferred exceeds "32767" (Error code: K6706).
At this time, the data up to the last device number of "R32767"
*1
is read (transferred).
2) When a memory cassette is not connected. (Error code: K6771)
*2
3) When the protect switch of the memory cassette is set to ON. (Error code: K6770)
*1. For the FX
3G and FX3GC PLCs, the last device number is "23999".
*2. This does not cause an error with the FX
3G PLCs because the PLCs read the contents of the
extension file registers stored in the PLC's built-in EEPROM even if a memory cassette is not
connected.