Arria V GZ Avalon-ST Interface for PCIe Solutions: User Guide

ID 683297
Date 12/21/2020
Public
Document Table of Contents

7.1.4. Legacy Interrupts

Legacy interrupts mimic the original PCI level-sensitive interrupts using virtual wire messages. The Arria® V GZ signals legacy interrupts on the PCIe link using Message TLPs. The term, INTx, refers collectively to the four legacy interrupts, INTA#, INTB#, INTC# and INTD#. The Arria® V GZ asserts app_int_sts to cause an Assert_INTx Message TLP to be generated and sent upstream. Deassertion of app_int_sts causes a Deassert_INTx Message TLP to be generated and sent upstream. To use legacy interrupts, you must clear the Interrupt Disable bit, which is bit 10 of the Command register. Then, turn off the MSI Enable bit.

The following figures illustrates interrupt timing for the legacy interface. The legacy interrupt handler asserts app_int_sts to instruct the IP to send a Assert_INTx message TLP.

Figure 41. Legacy Interrupt Assertion

The following figure illustrates the timing for deassertion of legacy interrupts. The legacy interrupt handler asserts app_int_sts causing the IP to send a Deassert_INTx message.