Interrupts

• Each device has 1-bit “arm’ register to be set by software if interrupt from the device to be accepted.

• CCR is used to program the interrupts

• A good design should provide for extensibility in the number of devices that can issue interrupts and also number of ISRs.

• Either polled or vectored interrupts depending on nature of processors and I/O devices.

  • Polling: Dedicated controllers, data acquisition with periodicity and the I/O devices are slow
  • Interrupts: Real-time environments, when events are unpredictable and asynchronous

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