26.8.3.3 Interrupt Vectoring

The interrupt handler address corresponding to the interrupt source selected by the INTSEL field can be stored in AIC_SVR (Source Vector register). When the processor reads AIC_IVR, the value written into AIC_SVR corresponding to the current interrupt is returned. Optionally, the AIC_IVR register can return the current interrupt number instead. This can be defined separately for each interrupt source using the AIC SVR Return Enable Register (AIC_SVRRER) and AIC SVR Return Disable Register (AIC_SVRRDR).

This feature offers a way to branch in one single instruction to the handler corresponding to the current interrupt, as AIC_IVR is mapped at the absolute address 0xFFFFF100 and thus accessible from the ARM interrupt vector at address 0x00000018 through the following instruction:

LDR PC,[PC,# -&F20]

When the processor executes this instruction, it loads the read value in AIC_IVR in its program counter, thus branching the execution on the correct interrupt handler.