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System Reset and Initialization
2-12
System Resets, Interrupts, and Operating Modes
Return From Interrupt
The interrupt handling routine terminates with the instruction:
RETI (return from an interrupt service routine)
The return from the interrupt takes 5 cycles to execute the following actions
and is illustrated in Figure 2−8.
1) The SR with all previous settings pops from the stack. All previous settings
of GIE, CPUOFF, etc. are now in effect, regardless of the settings used
during the interrupt service routine.
2) The PC pops from the stack and begins execution at the point where it was
interrupted.
Figure 2−8. Return From Interrupt
Item1
Item2
SP TOS
Item1
Item2
SP TOS
PC
SR
Before After
PC
SR
Return From Interrupt
Interrupt Nesting
Interrupt nesting is enabled if the GIE bit is set inside an interrupt service
routine. When interrupt nesting is enabled, any interrupt occurring during an
interrupt service routine will interrupt the routine, regardless of the interrupt
priorities.