Attention

IronPLC can only run very simple programs. The steps described are accurate but many language features are not yet supported.

SR

Set-dominant bistable function block. A flip-flop where the set input takes priority: if both S1 and R are TRUE, the output Q1 is TRUE.

IEC 61131-3

Section 2.5.2.3.1

Support

Supported

Inputs

Name

Type

Description

S1

BOOL

Set input (dominant)

R

BOOL

Reset input

Outputs

Name

Type

Description

Q1

BOOL

Output state

Behavior

The output is computed as Q1 := S1 OR (NOT R AND Q1). When S1 is TRUE, the output is set regardless of R. When only R is TRUE, the output is cleared. The output retains its value between scans (latching).

Example

This example shows that set dominates: both S1 and R are TRUE, yet output is TRUE.

See Also

  • RS — reset-dominant bistable