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Registered: ‎08-06-2017

What's the Legacy IRQ/FIQ?

1.png        Excuse me, in the Figure7-3, I am not very clear what the Legacy IRQ/FIQ is. What's the difference between the Legacy IRQ/FIQ and the GIC Interrupt Distributor? 

        In order to test the Pass-Through Mode, I have enable the CPU0-IRQ and CPU0-FIQ in the Block Design, and according to the Table 7-1, I set the register ICCICR to  0x00000000 or  0x00000008 , however, the two Interrupts can't occur.

                                             Xil_Out32(IntcConfig->CpuBaseAddress, 0x00000000) 

                                             Xil_Out32(IntcConfig->CpuBaseAddress, 0x00000008)

when I set the register ICCICR to  0x0000000B,  Both the  CPU0-IRQ and CPU0-FIQ can occur. So it seems that both the interrupts only can interrupt the CPU0 through the GIC, and the Pass-through Mode doesn't work.



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Scholar drjohnsmith
Registered: ‎07-09-2009

Re: What's the Legacy IRQ/FIQ?

Im a Hardware guy, so this is a real simple statement,,


but what I can point you at, is its pure ARM.


Older ARMs , traditional had two interrupts, fast and "not so fast". FIQ basicaly clobbered the IRQ for the sake of speed,


OK, SW guys will LOL, but..


Modern ARM processors, as you have seen, have more complicated interrupts    

     vector based and all that sort of stuff


Unless the newer interrupts don't do what you want, don't worry. 


this might help



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Registered: ‎08-06-2017

Re: What's the Legacy IRQ/FIQ?

Thanks for your reply.But I may not enquire the difference between FIQ and IRQ. I  just want to know how to generate a legacy interrupt. 

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