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CHAPTER 19 INTERRUPT FUNCTIONS
User’s Manual U15798EJ2V0UD
Figure 19-13. Nesting Examples (2/2)
Example 3. Nesting does not occur because interrupt is not enabled
Interrupt is not enabled during servicing of interrupt INTxx (EI instruction is not issued), therefore, interrupt request
INTyy is not acknowledged and nesting does not take place. The INTyy interrupt request is held pending, and is
acknowledged following execution of one main processing instruction.
PR = 0: Higher priority level
IE = 0:
Interrupt request acknowledgment disabled
Main processing
INTxx servicing INTyy servicing
EI
1 instruction execution
RETI
RETI
INTxx
(PR = 0)
INTyy
(PR = 0)
IE = 0
IE = 0
IE = 1
IE = 1