MC-Basic:SEMAPHORETAKE

SEMTAKE acquires a semaphore that can be used for multi-task synchronization. If a semaphore is free, SEMTAKE returns 1 and the semaphore is marked as ‘taken’. If the semaphore is already taken, SEMTAKE returns 0 and the semaphore’s status does not change. SEMTAKE can be used to block simultaneous access to shared resources in the system or to a critical user software section.

If time-out is provided system will try to acquire a semaphore specified amount of time.

Short form

semTake

Syntax

<lval> = SemTake(<semaphore name> { , <timeout>})

Availability

Versions 3.7.x and higher

Type

Long

Range

return value:          0 = unsuccessful (semaphore not taken)

1 = succeessful (semaphore taken)

<timeout>:             0 to 5000

Units

milliseconds

Default

0

Scope

Task, Terminal

Examples

While semTake(SEM1,1000) = 0                ‘wait for the release of the semaphore
’wait for resource   

End While

REM critical section code

……

……

semTake(SEM1)                                         ‘take the semaphore

semTake(SEM1 , 100 )

See Also

• SEMAPHOREGIVE