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Honored Contributor I

About PCI Express generate a "Interrupt request" to Nios(Use DE2i-150)

Now I want to extend the project "pcie_fundamental" in system CD, but I meet some problems in software and Qsys part. 

My target is generate a "interrupt" from PCIE at PC host, and deal with it in "nios ii for eclipse". 


As shown in appendix "Qsys.JPG", I connect "PCIE Hard IP Compiler" and "Nios Processor" in IRQ(Interrupt request). 

(If it has a connect error, please tell me.) 




These are my questions: 


1. How to generate a "interrupt request" from PCI Express to Nios? 


2. Could I use below method to generate "Interrupt request"? 






Article mentioned that "Enables assertion of Avalon-MM interrupt CraIrq_o signal when the specified mailbox is written by the root complex".  


How to enable "interrupt to Avalon MM", like this below(This C++ code in software part, and i try to enable P2A_MB_IRQ[0])? 

(If it has a any error, please tell me.) 




3. If above mentioned part is right, how to handle "Interrupt" when Nios II receive a IRQ(interrupt request queue)?  

Could I register a ISR(Interrupt Service Routine) like below? 


alt_irq_register(PCIE_HARD_IP_IRQ, 0, ISR); 


Now I focus on What is PCI Express generate a interrupt request and Nios how to receive interrupt and how to handle it? 


Appendixes "Qsys part" and "software part" can help you realize my question. 


Qsys Part: 

Software Part: 

(software part is use in PC host, not in use in "Nios II for Eclipse") 


IP Compiler for PCI Express User Guide: (

DE2i_150 FPGA System User Manual: 



Sincerely yours, Williams
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Honored Contributor I

I don't think PCI express was designed for the PC to send an interrupt to the card. You might be able to write some HDL code to generate an interrupt to your processor when a specific address on the card is written to by the PC.

Honored Contributor I

Write HDL code is a method, but I want to know how to use "Generate a 'Avalon-MM Interrupt' " about PCI express Hard IP compiler. 


Could you give me some example?