Intel® Stratix® 10 Hard Processor System Technical Reference Manual

ID 683222
Date 11/28/2022
Public

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17.6.2.7. Interrupts

Interrupts can be generated as a result of various events. The DMA Register 5 (Status Register) contains a status bit for each of the events that can cause an interrupt. Register 7 (Interrupt Enable Register) contains an enable bit for each of the possible interrupt sources.

There are two groups of interrupts, Normal and Abnormal, as described in Register 5 (Status Register). Interrupts are cleared by writing a 1 to the corresponding bit position. When all the enabled interrupts within a group are cleared, the corresponding summary bit is cleared. When both the summary bits are cleared, the sbd_intr_o interrupt signal is deasserted. If the MAC is the cause for assertion of the interrupt, then any of the GLI, GMI, TTI, or GLPII bits of Register 5 (Status Register) are set to 1.

Figure 82.  Summary Interrupt (sbd_intr_o) Generation
Note: Register 5 (Status Register) is the interrupt status register. The interrupt pin (sbd_intr_o) is asserted because of any event in this status register only if the corresponding interrupt enable bit is set in Register 7 (Interrupt Enable Register). 

Interrupts are not queued, and if the interrupt event occurs before the driver has responded to it, no additional interrupts are generated. For example, Bit 6 (Receive Interrupt) of Register 5 (Status Register) indicates that one or more frames were transferred to the Host buffer. The driver must scan all descriptors, from the last recorded position to the first one owned by the DMA. 

An interrupt is generated only once for multiple, simultaneous events. The driver must scan Register 5 (Status Register) for the cause of the interrupt. After the driver has cleared the appropriate bit in Register 5 (Status Register), the interrupt is not generated again until a new interrupting event occurs. For example, the controller sets Bit 6 (Receive Interrupt) of Register 5 (Status Register) and the driver begins reading Register 5 (Status Register). Next, the interrupt indicated by Bit 7 (Receive Buffer Unavailable) of Register 5 (Status Register) occurs. The driver clears the receive interrupt (bit 6). However, the sbd_intr_o signal is not deasserted, because of the active or pending Receive Buffer Unavailable interrupt. 

Bits 7:0 (riwt field) of Register 9 (Receive Interrupt Watchdog Timer Register) provide for flexible control of the receive interrupt. When this Interrupt timer is programmed with a non-zero value, it gets activated as soon as the RX DMA completes a transfer of a received frame to system memory without asserting the receive Interrupt because it is not enabled in the corresponding Receive Descriptor (RDES1[31]). When this timer runs out as per the programmed value, the AIS bit is set and the interrupt is asserted if the corresponding AIE is enabled in Register 7 (Interrupt Enable Register). This timer is disabled before it runs out, when a frame is transferred to memory, and the receive interrupt is triggered if it is enabled.

Signals NIS and AIS are registered.