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Interrupts Tutorial


The microprocessor system may be measuring temperatures in the Sahara desert. Once a year it receives a radio signal telling it to stop measuring temperatures and send all last year's data to base. This is an INTERRUPT.

The CPU completes it current instruction. It then pushes any data it wishes to save onto the stack. It then jumps to a routine which services the interrupt. Once the interrupt routine is completed, it pulls the saved data from the stack and carries on measuring temperatures. There are two pins on the CPU which, when taken low, cause a hardware interrupt.

IRQ can be sensed or ignored depending the value of the interrupt flag in the status register.

NMI cannot be ignored.

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