Mitsubishi Electric MELSEC-L LD75P User Manual page 637

(b) Writing to the flash ROM can be executed up to 100,000 times.
If writing to the flash ROM exceeds 100,000 times, the writing may become impossible.
(c) After the power ON and CPU module reset operation, writing to the flash ROM using
a program is limited to up to 25 times. (Not limited to up to 25 times when writing to
the flash ROM is carried out by GX Works2.)
If the 26th writing is requested after the power ON/CPU module reset operation, the error "Flash ROM write
number error" (error code: 805) will occur, and the writing will be disabled.
If a flash ROM write error occurs by one writing to the flash ROM, check and correct the flash ROM writing
program.
Then reset the error or turn ON the power and reset the CPU module again.
(d) The ZP.PFWRT instruction can only be executed when the LD75 READY signal (X0)
is turned OFF.
When the LD75 READY signal is turned ON, the ZP.PFWRT instruction cannot be executed.
Before executing the ZP.PFWRT instruction, turn OFF the PLC READY signal (Y0) and then turn OFF the
LD75 READY signal.
CHAPTER 14 DEDICATED INSTRUCTIONS
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