Mitsubishi MELSEC-A Series Programming Manual page 20

2. INSTRUCTIONS
6)..... Indicates the execution condition of each instruction and details are as
described below:
Symbol
Instruction which is always executed regardless of ON/OFF of the preceding condition.
No entry
If the preceding condition is OFF, that instruction executes an OFF processing.
Instruction which is executed during ON. Executes instruction only while the preceding
condition of that instruction is on. When the preceding condition is off, that instruction
is not executed and not processed.
Instruction which is executed once during ON. Executes instruction only at the positive
transition of the preceding condition of instruction, i.e. the condition changes from off to
on. Thereafter, even if the condition is on, that instruction is not executed and not
processed.
Instruction which is executed once during OFF. Executes instruction only at the
negative transition of the preceding condition of instruction, i.e. the condition changes
from on to off. Thereafter, even is the condition is off, that instruction is not executed
and not processed.
7)..... Indicates the number of steps of each instruction. The number of steps, which
change depending on conditions, is indicated in two stages. For details, refer
to each instruction.
POINT
If extension devices are used or index qualification is performed with bit
devices in the case of the instructions which need device specification for the
AnA, A2AS, AnU, QCPU-A (A Mode) and A2USH board, the number of steps
increases. Refer to Section 3.8.1 for details.
8)..... The mark indicates that the instruction can be indexed (Z, V).
The mark indicates that the instruction can be indexed with the AnA, A2AS,
AnU, QCPU-A (A Mode) and A2USH board only.
9)..... The mark indicates that the instruction is a subset instruction.
The mark indicates that the subset processing can be performed with the
A3H, A3M, AnA, A2AS, AnU, QCPU-A (A Mode) and A2USH board only.
10)... Indicates applicable CPU.
The ! mark indicates that it is applicable to all types of CPUs.
The mark indicates that it is applicable to some types of CPUs.
The  mark indicates that it is applicable to specific CPUs.
11).... Indicates a page which explains each instruction.
Execution Condition
2 − 4
MELSEC-A