H a r d w a r e I n t e r r u p t s

Interrupt Status Register Enabled. Identifies the current state of all interrupt sources that are enabled. This register is defined by performing a logical AND of the Interrupt Status Register Raw and the Interrupt Enable register. All bits in the Interrupt Status Register Enabled are ORed together. The output is fed directly to the IRQ line, which then interrupts the ARM.

Interrupt sources

Each interrupt source is enabled and disabled within its respective module (and submodule) within the NS7520 ASIC. The interrupt controller in the GEN module, however, does not latch any of the interrupt signals.

Note: Interrupt causes are latched in their respective submodule until cleared. Interrupt sources include the following:

DMA interrupts. All [13] DMA channels, including the four sub-channels of the Ethernet receiver, have five possible interrupt sources. See Chapter 8, "DMA Module."

Ethernet receive and transmit interrupts. There are three interrupts for Ethernet receive and four interrupts for Ethernet transmit; all interrupts are part of the Ethernet General Status register. These interrupts are used only when the Ethernet receiver and transmitter are in interrupt mode rather than DMA mode. See Chapter 9, "Ethernet Module."

Serial interrupts. The Serial Channel Status register has many interrupt sources. See Chapter 10, "Serial Controller Module."

Watchdog timer interrupts. When the watchdog timer expires, the system can generate either an IRQ interrupt, an FIRQ interrupt, or a system reset. The interrupt type and length of the timer are configured using the GEN module System Control register. The watchdog is strobed using the Software Service register. See Chapter 6, "GEN Module."

Timer 1 and Timer 2 interrupts. Two types of interrupts can be generated by Timers 1 and 2. The interrupt type is configured in the Timer Control register; the interrupt itself is contained within the Timer Status register. See Chapter 6, "GEN Module."

4 0

N S 7 5 2 0 H a r d w a r e R e f e r e n c e , R e v . D 0 3 / 2 0 0 6

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Digi NS7520 manual Interrupt sources