S5 AWL Command: NOP (No Operation)
S5 AWL instruction NOP 0 / NOP 1: No operation. Used as jump target placeholder and for program alignment.
S5 AWL Command: NOP 0 / NOP 1 (No Operation)
NOP performs no operation. It is used as a placeholder — typically as a label target for jump instructions.
Syntax
NOP 0 // No operation (word = 0000 hex)
NOP 1 // No operation (word = FFFF hex)
S7 Equivalent
| S5 AWL | S7 STL | S7 SCL |
|---|---|---|
| NOP 0 | NOP 0 | Not needed |
| NOP 1 | NOP 1 | Not needed |
Typical Use
U E 0.0
SPB =M001
// ... some code ...
SPA =M002
M001: NOP 0 // Jump target — NOP is just a landing pad
// ... other code ...
M002: NOP 0 // Another jump target
NOP 0 does nothing but provides a valid address for a jump label. In SCL, there is no equivalent — IF/THEN/ELSE structures do not need landing pads.
NOP 0 vs. NOP 1
The difference is only the bit pattern stored in memory: NOP 0 = all zeros (0x0000), NOP 1 = all ones (0xFFFF). Functionally identical. NOP 1 is sometimes found in erased EPROM areas (where all bits default to 1).
Part of the S5 AWL Command Reference. Maintained by PLCcheck.ai.
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