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Lecture22 - 0306-250 Assembly Language Programming Lecture...

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0306-250 Assembly Language Programming Lecture Twenty-Two: Hardware Interrupts (Text Chapter 12)
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Peripheral/CPU Interaction 2 Initialization: peripheral device configured as needed Operating modes – Polling – Interrupt Shutdown: peripheral device disabled
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Device Polling Operating Mode 3 CPU-driven service CPU examines device status Periodically Continually CPU determines if device requires service Delayed service time Depends on CPU polling interval
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Device Interrupt Operating Mode 4 Peripheral device-driven service Peripheral device determines it needs service Peripheral device then notifies CPU Immediate service time CPU acts on interrupt
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Interrupt Somewhat like Subroutine 5 Similarities Called to handle task Stack used in handling Differences Called via signal attached to CPU Can occur at any time
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Hardware Interrupts 6 Calling mechanism: Interrupt request (IRQ) line Analog of BSR/JSR for subroutine Called code: Interrupt service routine (ISR) Analog of subroutine for interrupt
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