Interrupts

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What happens? • So what happens when an interrupt (IRQ) occurs? 1/4/2010 8. Then the ISR is executed 1. The INT0 flag in EIFR is cleared 2. If there are any “pushes”, they get executed 9. The remainder of the ISR is executed until (almost) the end 10. Anything pushed onto the stack is popped off in the reverse order 11. The global interrupt flag in the status register is set again to re-enable interrupts 12. The RTI instruction is executed 1. The INT0 flag in EIFR is set again 13. The “old” address is popped off the stack and loaded into the PC 14. Main program continues execution where it left off 32
Summary • In this topic we: – Became familiar with interrupts on the AVR • Maskable and non-maskable • Initialization • Triggers – Developed an interrupt service routine – Discussed the sequence of events that occur when an IRQ occurs 1/4/2010 33
Page 1 and 2: Microprocessor Fundamentals Topic 1
Page 3 and 4: Interrupts • Interrupts are async
Page 5 and 6: Maskable/Non-maskable • Interrupt
Page 7 and 8: EICRA INT3 - 0 • External Interru
Page 9 and 10: EICRA INT3 - 0 1/4/2010 Exercise: W
Page 11 and 12: Pins • INT3:0 External Interrupts
Page 13 and 14: Pins • INT3:0 When the appropriat
Page 15 and 16: Pins • INT3:0 Exercise: I want to
Page 17 and 18: Pins • Bits 7 - 4 External Interr
Page 19 and 20: Vectors The complete vector table i
Page 21 and 22: An Example: • So, let’s work th
Page 23 and 24: An Example: We must start our progr
Page 25 and 26: An Example: We need to write the in
Page 27 and 28: An Example: We must start our progr
Page 29 and 30: An Example: Then we must write the
Page 31: What happens? • So what happens w

Interrupts

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