in arm7tdmi, when FIQ and RIQ occures at same time so how both are executed sequentially,first FIQ and thenIRQ?

in arm7tdmi, suppose instruction is being executed and at same time FIQ and IRQ both occur  at same time.now according to priority FIQ will be handled then IRQ  but my question is that how it will handled IRQ after  return from FIQ i