SPRUJB3 March 2024 AM67 , AM67A , TDA4AEN-Q1 , TDA4VEN-Q1
The End Point (EP) can trigger generation of a PCI Legacy Interrupt at the Root Complex via an in-band Assert_INTx / Deassert_INTx messages (where x = A, B, C, or D). Software can write to the PCIE_USER_LEGACY_INTR_SET register to trigger the required INTx (where x = A, B, C, or D) assert and de-assert message from the PCIe core. Once an assert message has been generated, it cannot be generated again until a deassert message is generated. Thus, only one interrupt can be pending at a time.
There is no hardware input port provided that will allow generation of legacy interrupts on the EP port.
The interrupt messaging mechanism makes it unfeasible to guarantee a time of delivery of the interrupt unlike in conventional designs where the interrupt line is often electrically connected to the final destination.