SEMA
Inputs
|
Input |
Data type |
Description |
|
CLAIM |
BOOL |
Takes the semaphore. |
|
RELEASE |
BOOL |
Releases the semaphore. |
Outputs
|
Output |
Data type |
Description |
|
BUSY |
BOOL |
TRUE if semaphore is busy. |
Remarks
The function block implements the following algorithm:
BUSY := mem;
if CLAIM then
mem := TRUE;
else if RELEASE then
BUSY := FALSE;
mem := FALSE;
end_if;
In LD language, the input rung is the CLAIM command. The output rung is the BUSY output signal.
ST Language
MySema is a declared instance of SEMA function block:
MySema (CLAIM, RELEASE);
BUSY := MySema.BUSY;
FBD Language
LD Language
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