NEC 78K0S/KA1+ User Manual page 225

Main processing
INTxx
During interrupt INTxx servicing, interrupt request INTyy is acknowledged, and multiple interrupts are generated.
Before each interrupt request acknowledgement, the EI instruction is issued, the interrupt mask is released, and the
interrupt request acknowledgement enable state is set.
Caution Multiple interrupts can be acknowledged even for low-priority interrupts.
Example 2. Multiple interrupts are not generated because interrupts are not enabled
Main processing
EI
INTxx
Because interrupts are not enabled in interrupt INTxx servicing (the EI instruction is not issued), interrupt request
INTyy is not acknowledged, and multiple interrupts are not generated. The INTyy request is held pending and
acknowledged after the INTxx servicing is performed.
IE = 0: Interrupt request acknowledgment disabled
CHAPTER 12 INTERRUPT FUNCTIONS
Figure 12-10. Example of Multiple Interrupts (1/2)
Example 1. Multiple interrupts are acknowledged
IE = 0
EI
INTyy
INTxx servicing
IE = 0
INTyy
IE = 0
User's Manual U16898EJ3V0UD
INTxx servicing
IE = 0
EI
RETI
RETI
INTyy servicing
RETI
INTyy servicing
INTyy is held pending
RETI
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