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MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
429
Preliminary—Subject to Change Without Notice
request to the processor is asserted. The INTVEC field retains that value until the next time the interrupt
request to the processor is asserted. The rest of the handshaking is described in
”.
14.6.3.1.2
End of Interrupt Exception Handler
Before the interrupt exception handling completes,
Section 14.5.10, “INTC Software Set/Clear Interrupt
Registers (INTC_SSCIR0_3 - INTC_SSCIR4_7)
” must be written. When it is written, the associated
LIFO is popped so that the preempted priority is restored into PRI of the associated INTC_CPR_PRC0 or
INTC_CPR_PRC1. Before it is written, the peripheral or software setable flag bit must be cleared so that
the peripheral or software setable interrupt request is negated.
NOTE
Depending on the pipelining on an SoC implementation’s pipelining
capabilities and bus architecture, a store to clear the peripheral or software
setable interrupt flag bit which closely precedes the store to the
INTC_EOIR_PRC0 or INTC_EOIR_PRC1 can result in that peripheral or
software setable interrupt request being serviced again. If this scenario can
happen, preventative measures can be used such as executing a Power
Architecture isync instruction before the store to the INTC_EOIR_PRC0 or
INTC_EOIR_PRC1 as shown in
Section 14.7.2.1, “Software Vector
When returning from the preemption, the INTC does not search for the peripheral or software setable
interrupt request whose ISR was preempted. Depending on how much the ISR progressed, that interrupt
request may no longer even be asserted. When PRI in the associated INTC_CPR_PRC0 or
INTC_CPR_PRC1 is lowered to the priority of the preempted ISR, the interrupt request for the preempted
ISR or any other asserted peripheral or software setable interrupt request at or below that priority will not
cause a preemption. Instead, after the restoration of the preempted context, the processor will return to the
instruction address that it was to next execute before it was preempted. This next instruction is part of the
preempted ISR or the interrupt exception handler’s prolog or epilog.