Mitsubishi Electric MELSEC-Q Series User Manual page 122

7 FUNCTION
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(2) Precautions
Take a note of the following when writing during RUN:
(a) The memory that can be written during RUN is only program memory.
If the write during RUN is performed while booting a program from the
standard ROM, the program to be booted will not be changed.
Write the contents of the program memory to the standard ROM before
powering off the PLC or resetting the Basic model QCPU.
(b) A maximum of 512 steps can be written at once during RUN.
(c) Normal operation will not be performed if any of the following instructions is
written using online write.
1) Trailing edge instructions
Any of the following trailing edge instructions is executed if the
execution condition of the trailing edge instruction is OFF on
completion of write.
• LDF
• ANDF
• ORF
• MEF
• PLF
2) Leading edge instructions
The leading edge instruction is not executed if the execution condition
of the leading edge instruction (PLS instruction/ P instruction) is ON
on completion of write.
The leading edge instruction is executed when the execution condition
turns from OFF to ON again.
3) SCJ instruction
If the execution condition of the SCJ instruction is ON on completion of
write, a jump to the specified pointer is made without waiting for one
scan.
MELSEC-Q
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