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CSE3306

CSE3306. Lecture: 12 Title: Interrupts. Today's Topics. Demonstrate Timer Interrupt Critical Sections 8259 PIC ISR Scheduling. Timer Interrupt Demonstration. Program Overview Install on IRQ0 (INT 8) Call Original Timer Interrupt Increments Count=0..18

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CSE3306

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  1. CSE3306 Lecture: 12 Title: Interrupts CSE3306--L12

  2. Today's Topics • Demonstrate Timer Interrupt • Critical Sections • 8259 PIC • ISR Scheduling CSE3306--L12

  3. Timer Interrupt Demonstration • Program Overview • Install on IRQ0 (INT 8) • Call Original Timer Interrupt • Increments Count=0..18 • Increments SecCount when Count=18 • Running Program prints SecCount • Termination Restores Interrupt CSE3306--L12

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  7. Critical Sections • STI: SeT Interrupt enableAllow other routines to be serviced • CLI: CLear Interrupt enable Retain full control of CPU CSE3306--L12

  8. 8259 PIC (Programmable Interrupt Controller) • Latches incoming interrupt signals (IRQ signal) • Allows masking interrupts (except NMI) • Prioritizes Interrupts (IRQ 0==Highest) • IF (interupt unmasked) AND (interrupt flag=1) AND (not servicing higher interrupt) THEN call interrupt CSE3306--L12

  9. ISR Scheduling CSE3306--L12

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