Back to FBD referenceTypical FBD symbol for AND
Basic logic
AND
Logical AND
The AND block combines two conditions. Output Q becomes TRUE only when IN1 and IN2 are both TRUE.
Typical FBD symbol
IN1
IN2
AND
Q
Inputs
| Name | Type | Required | Description |
|---|---|---|---|
| IN1 | BOOL | Yes | The first boolean condition. |
| IN2 | BOOL | Yes | The second boolean condition. |
Outputs
| Name | Type | Required | Description |
|---|---|---|---|
| Q | BOOL | Yes | The logical AND result. |
Stateful
No, the block does not keep internal state.
Behavior rule
Q = IN1 AND IN2
Truth table
| IN1 | IN2 | Q |
|---|---|---|
| FALSE | FALSE | FALSE |
| FALSE | TRUE | FALSE |
| TRUE | FALSE | FALSE |
| TRUE | TRUE | TRUE |
Practical use
- permit start only when the start button is pressed and the safety door is closed;
What to watch
- Assuming one active input is enough. For AND, both inputs must be TRUE.