RM0453 Rev 5 377/1450
RM0453 Hardware semaphore (HSEM)
385
Figure 35. Interrupt state diagram
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:
– 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.
On semaphore x free interrupt, try to lock semaphore x
• If the semaphore lock is obtained:
Disable the semaphore x interrupt in HSEM_CnIER.
Clear pending semaphore x interrupt status in HSEM_CnICR.
• If the semaphore x lock fails:
Clear pending semaphore x interrupt status in HSEM_CnICR.
Try again to lock the semaphore x:
– If the semaphore lock is obtained (semaphore has been freed between first try to
lock and semaphore interrupt status clear), disable the semaphore interrupt in
HSEM_CnIER.
MS40533V3
Semaphore x
locked
Semaphore x free
WRITE
(COREID & PROCID & LOCK = 0)
Interrupt
Semaphore x
Enabled
Interrupt
Semaphore x
MaskedStatus = 1 & Interrupt generated
Interrupt
Semaphore x
Status = 1
Yes
No
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