Short summary

Name	`SR`
→POU type	→function block
Category	IEC-block, Bistable
Conform to →IEC-standard	no restrictions
Graphical interface
Available since	version 1.18.0 (for logi.CAD 3)

Functionality

The block serves for short-term or lasting storage of logical states. Hence it is the equivalent to the seal-in circuit known in the contactor technique .

→Turning input S1 on triggers output Q1 to return value TRUE (or an equivalent). Turning input R on triggers output Q1 to return value FALSE (or an equivalent). The identification S1 indicates that this input is dominant.

In-/outputs

	Identifier	→Data type	Description
Inputs:	`S1`	`BOOL`	set (dominant)
Inputs:	`R`	`BOOL`	reset
Outputs:	`Q1`	`BOOL`

Input EN and output ENO are available when →calling the block. See "Execution control: EN, ENO" for information on input EN and output ENO.

See:

"Blocks for safe logic" whether this block is supported for developing safety-relevant applications.
"Highlighting safe logic in the FBD-editor" for the effects when using the block as a block for safe logic .

Example for usage within ST-editor

PROGRAM Test
    VAR
        DB_On     : SR;
        Out       : BOOL;
        TriggerS1 : BOOL;
        TriggerR  : BOOL;
    END_VAR
 
    DB_On(S1 := TriggerS1, R := TriggerR, Q1 => Out);
    (* Instance of block 'SR' is called. *)
    (* Input 'S1' gets value from 'TriggerS1' variable. Input 'R' gets value from 'TriggerR' variable.*) 
    (* Output 'Q' returns TRUE, if 'TriggerS1' is TRUE. Output 'Q' returns FALSE, if 'TriggerR' is TRUE and 'TriggerS1' is FALSE. *)
    (* Variable 'Out' accesses the output 'Q1'. *)
END_PROGRAM

When creating your application within the ST-editor, enter a call of a block by typing the text as requested by the syntax or use Content Assist.