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CHAPTER 19 INTERRUPT FUNCTIONS
Figure 19-14. Multiple Interrupt Examples (2/2)
Example 3. Multiple interrupt servicing does not occur because interrupt is not enabled
Main processing
INTxx servicing INTyy servicing
EI
1 instruction execution
RETI
RETI
INTxx
(PR = 0)
INTyy
(PR = 0)
IE = 0
IE = 0
Interrupt is 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 acknowledge disable
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