sema

 Function Block - Semaphore.

The function block implements this algorithm:

    BUSY := mem;
    if CLAIM then
       mem := TRUE;
    else if RELEASE then
       BUSY := FALSE;
       mem := FALSE;
    end_if;

Inputs

Input	Data Type See Data Types.	Range	Unit	Default	Description
CLAIM	BOOL	FALSE, TRUE			Takes the semaphore.
RELEASE	BOOL	FALSE, TRUE			Releases the semaphore.

Outputs

Output	Data Type See Data Types.	Range	Unit	Description
BUSY	BOOL	FALSE, TRUE		TRUE if semaphore is busy.

FBD Language Example

FFLD Language Example

• In the FFLD Language, the input rung is the CLAIM command.
  • The output rung is the BUSY output signal.

IL Language Example

Not available.

ST Language Example

(* MySema is a declared instance of SEMA function block *)
MySema (CLAIM, RELEASE);
BUSY := MyBlinker.BUSY;