Short summary

Name	`SEMA`
→POU type	→function block
Category	IEC-block, BistableEnh
Conform to →IEC-standard	not defined in IEC-standard
Graphical interface
Available since	version 1.27.0 (for logi.CAD 3)

Functionality

The block represents a semaphore.

If input CLAIM is →turned on, output BUSY returns value TRUE (or an equivalent) starting with the next executed cycle. If input RELEASE is turned on, output BUSY returns value FALSE (or an equivalent) .

In-/outputs

	Identifier	→Data type	Description
Inputs:	`CLAIM`	`BOOL`	set (dominant)
Inputs:	`RELEASE`	`BOOL`	reset
Outputs:	`BUSY`	`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.

Example for usage within ST-editor

PROGRAM Test
   VAR
      mySEMA   : SEMA;
      TriggerC : BOOL;
      TriggerR : BOOL;
      Out      : BOOL;
   END_VAR
   mySEMA(CLAIM := TriggerC, RELEASE := TriggerR, BUSY => Out);
   (* Instance of block 'SEMA' is called. *)
   (* Input 'CLAIM' gets value from 'TriggerC' variable. Input 'RELEASE' gets value from 'TriggerR' variable.*)
   (* Output 'BUSY' returns TRUE, if 'TriggerC' is TRUE. Output 'BUSY' returns FALSE, if 'TriggerR' is TRUE and 'TriggerC' is FALSE. *)
   (* Variable 'Out' accesses the output 'BUSY'. *)
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.