NEC 78K0 User Manual page 444

Example 3. Multiple interrupt servicing does not occur because interrupts are not enabled
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 acknowledgment disabled
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CHAPTER 19 INTERRUPT FUNCTIONS
Figure 19-10. Examples of Multiple Interrupt Servicing (2/2)
Main processing
IE = 0
EI
INTxx
(PR = 0)
IE = 1
1 instruction execution
User's Manual U15947EJ2V0UD
INTxx servicing INTyy servicing
INTyy
(PR = 0)
RETI
IE = 0
RETI
IE = 1
*