S5 AWL Command: O (OR)
S5 AWL instruction O (OR): Syntax, S7 equivalent, code examples. OR bit logic operation for the VKE.
S5 AWL Command: O (OR)
The O instruction performs a logical OR operation on the VKE. It reads a boolean operand and ORs it with the current VKE.
Syntax
O <operand>
S7 Equivalent
| S5 AWL | S7 STL | S7 SCL |
|---|---|---|
O E 0.1 | O I 0.1 (EN) / O E 0.1 (DE) | ... OR Input_0_1 |
In S7, O remains O in both English and German mnemonics.
Code Example
Two start buttons (either one starts the motor):
O E 0.0 // Start button 1
O E 0.1 // Start button 2
= A 4.0 // Motor on
AND before OR (implicit precedence in AWL):
U E 0.0 // Condition A1
U E 0.1 // Condition A2
O // OR (starts new AND branch)
U E 0.2 // Condition B1
U E 0.3 // Condition B2
= A 4.0 // Result: (A1 AND A2) OR (B1 AND B2)
Important: The standalone O (without operand) acts as an OR separator between AND chains. This is one of the most misunderstood AWL features.
Common Errors
Forgetting operator precedence: In AWL, AND (U) binds tighter than OR (O). The expression U E0.0 / O E0.1 / U E0.2 means E0.0 OR (E0.1 AND E0.2), NOT (E0.0 OR E0.1) AND E0.2. Use parentheses U( / ) or the standalone O to control precedence.
Related Commands
- ON (OR NOT) — OR with negation
- U (AND) — AND operation
Part of the S5 AWL Command Reference. Maintained by PLCcheck.ai.
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