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Why RETI instruction be the last instruction of ISR?

Why RETI instruction be the last instruction of ISR? Correct Answer because it returns to the main program where interrupt is generated and set the global interrupt enable bit in SREG

When an interrupt occurs, the global interrupt enable bit is cleared. If global interrupt enable is cleared it means interrupts are disabled. RETI instruction must last instruction of ISR because it returns to the main program where interrupt is generated and sets the global interrupt enable bit in SREG.

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