3.6.5. IRQ

The Interrupt Request (IRQ) exception is a normal interrupt caused by a LOW level on the nIRQ input. IRQ has a lower priority than FIQ and is masked out when a FIQ sequence is entered. It may be disabled at any time by setting the I bit in the CPSR, though this can only be done from a privileged (non-User) mode.

Irrespective of whether the exception was entered from ARM or THUMB state, an IRQ handler should return from the interrupt by executing:

SUBS PC, R14_irq, #4
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