NXP Semiconductors PXN2020, Reference Manual, Page: 426 / 1376

Semaphores
PXN20 Microcontroller Reference Manual, Rev. 1
15-14 Freescale Semiconductor
cores. The exact method for accessing the logical processor number varies by architecture. For Power
Architecture cores, there is a processor ID register (PIR) which is SPR 286 and contains this value. A
single instruction can be used to move the contents of the PIR into a general-purpose register:
mfspr rx,286
where rx is the destination GPRn. Other architectures may support a specific instruction to move the
contents of the logical processor number into a general-purpose register, e.g.,
rdcpn rx
for a read CPU
number instruction.
If the optional failed lock IRQ notification mechanisms are used, then accesses to the related registers
(SEMA4_CP
n INE, SEMA4_ CP n NTF) are required. There is no required negation of the failed lock write
notification interrupt as the request is automatically negated by the semaphores module once the gate has
been successfully locked by the failing processor.
Finally, in the event a system state requires a software-controlled reset of a gate or IRQ notification
register(s), accesses to the secure reset control registers (SEMA4_RSTGT, SEMA4_RSTNTF) are
required. For these situations, it is recommended that the appropriate IRQ notification enable(s)
(SEMA4_CP
n INE) bits be disabled before initiating the secure reset 2-write sequence to avoid any race
conditions involving spurious notification interrupt requests.
15.7 DMA Requests
There are no DMA requests associated with the IPS_Semaphore block.
15.8 Interrupt Requests
The semaphore interrupt requests are connected to the interrupt controller as described in Chapter 10,
Interrupts and Interrupt Controller (INTC).