220.127.116.11. External Interrupt Controller Interface
The EIC interface enables you to speed up interrupt handling in a complex system by adding a custom interrupt controller.
The EIC interface is an Avalon® -ST sink with the following input signals:
Signals are rising-edge triggered, and synchronized with the Nios II clock input.
The EIC interface presents the following signals to the Nios® II processor through the eic_port_data signal:
- Requested handler address (RHA)—The 32-bit address of the interrupt handler associated with the requested interrupt.
- Requested register set (RRS)—The six-bit number of the register set associated with the requested interrupt.
- Requested interrupt level (RIL)—The six-bit interrupt level. If RIL is 0, no interrupt is requested.
- Requested nonmaskable interrupt (RNMI) flag—A one-bit flag indicating whether the interrupt is to be treated as nonmaskable.
Table 66. eic_port_data Signal Bit Fields 44 ... RHA ... 13 12 11 10 9 8 7 6 5 4 3 2 1 0 RHA RRS RNMI RIL
Following Avalon® -ST protocol requirements, the EIC interface samples eic_port_data only when eic_port_valid is asserted (high). When eic_port_valid is not asserted, the processor latches the previous values of RHA, RRS, RIL and RNMI. To present new values on eic_port_data, the EIC must transmit a new packet, asserting eic_port_valid. An EIC can transmit a new packet once per clock cycle.
For an example of an EIC implementation, refer to the Vectored Interrupt Controller chapter in the Embedded Peripherals IP User Guide.
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