CHAPTER 16 INTERRUPT FUNCTIONS
Preliminary User’s Manual U16315EJ1V0UD
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Figure 16-10. Examples of Multiple Interrupt Servicing (2/2)
Example 3. Multiple interrupt servicing does not occur because interrupts are not enabled
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
Interrupts are not enabled during servicing of interrupt INTxx (EI instruction is not issued), therefore, interrupt
request INTyy is not acknowledged and multiple interrupt servicing 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 acknowledgement disabled
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