ST STM32WL55JC Reference Manual page 369

RM0453
The procedure to get an interrupt when a semaphore becomes free is described hereafter.
Try to lock semaphore x
•
If the semaphore lock is obtained, no interrupt is needed.
•
If the semaphore lock fails:
•
Clear pending semaphore x interrupt status for the interrupt line in HSEM_CnICR.
Re-try to lock the semaphore x again:
–
–
Figure 35. Interrupt state diagram
No
MaskedStatus = 1 & Interrupt generated
If the semaphore lock is obtained, no interrupt is needed (semaphore has been
freed between first try to lock and clear semaphore interrupt status).
If the semaphore lock fails, enable the semaphore x interrupt in HSEM_CnIER.
Semaphore x
locked
WRITE
(COREID & PROCID & LOCK = 0)
Interrupt
Semaphore x
Status = 1
Interrupt
Semaphore x
Enabled
Yes
Interrupt
Semaphore x
Semaphore x free
RM0453 Rev 2
Hardware semaphore (HSEM)
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