Mitsubishi MELSEC-A Series Programming Manual page 19

2. INSTRUCTIONS
3)..... Indicates the instruction symbol used for the program. The instruction symbol
is shown on a 16-bit instruction basis. The symbols of a 32-bit instruction and
an instruction executed only at the rise from OFF to ON are as indicated
below:
32-bit instruction.........D is added to the head of instruction.
Example:
16-bit instruction
Instruction executed only at the rise from OFF to ON.........P
is added to the end of instruction.
Example:
Instruction executed
during ON
4)..... Indicates the symbol diagram in the circuit.
Fig. 2.1 Symbol Representations in Ladder
Destination: Indicates the destination of data after operation.
Source: Stores data before operation.
5)..... Indicates the processing of each instruction.
(D) + (S) → (D)
Indicates 16 bits.
Fig. 2.2 Processing of Each Instruction
D +
+
32-bit instruction
+ P
+
Instruction executed only
at the rise from OFF to ON
Indicates destination.
Indicates source.
Indicates instruction
symbol.
16 bits, 16 bits
2 − 3
Indicates destination.
Indicates source.
Indicates instruction
symbol.
(D + 1, D) + (S + 1, S) → (D + 1, D)
Indicates 32 bits.
D + 1
Upper 16 bits
MELSEC-A
D
Lower 16 bits