RTEMS ITRON 3.0 API User's Guide
ER twai_sem( ID semid, TMO tmout );
E_OK - Normal Completion
E_ID - Invalid ID number (semid was invalid or could not be used)
E_NOEXS - Object does not exist (the semaphore specified by semid
does not exist)
E_OACV - Object access violation (A semid less than -4 was
specified from a user task. This is implementation dependent.)
E_PAR - Parameter error (tmout is -2 or less)
E_DLT - The object being waited for was deleted (the specified
semaphore was deleted while waiting)
E_RLWAI - Wait state was forcibly released (rel_wai was received
while waiting)
E_TMOUT - Polling failure or timeout exceeded
E_CTX - Context error (issued from task-independent portions or a
task in dispatch disabled state)
EN_OBJNO - An object number which could not be accessed on the
target node is specified.
EN_PAR - A value outside the range supported by the target node
and/or transmission packet format was specified as a parameter (a value
outside supported range was specified for tmout)
This routine attempts to acquire the semaphore specified by semid.
If the semaphore is available (i.e. positive semaphore count), then the
semaphore count is decremented and the calling task returns immediately.
Otherwise the calling tasking is blocked until the semaphore is released
by a subsequent invocation of sig_sem or the timeout period specified
by tmout milliseconds is exceeded. If the timeout period is exceeded,
then the E_TMOUT error is returned.
By specifiying tmout as TMO_FEVR, this routine has the same
behavior as wai_sem. Similarly, by specifiying tmout as
TMO_POL, this routine has the same behavior as preq_sem.
Multiprocessing is not supported. Thus none of the "EN_" status codes will be returned.
This routine may cause the calling task to block.
A clock tick is required to support the timeout functionality of this routine.
RTEMS ITRON 3.0 API User's Guide
Copyright © 1988-2004 OAR Corporation