Example Of Multiplexed Interrupt Servicing - NEC switch User Manual

Main processing
EI
INTxx
The interrupt request INTyy is acknowledged and multiplexed interrupt servicing is performed during the interrupt
INTxx servicing. Before each interrupt is acknowledged, the IE instruction is issued and interrupt requests are
enabled.
Example 2. Multiplexed interrupts are not performed because interrupts are disabled.
Main processing
EI
INTxx
Interrupt requests are disabled (EI instruction is not issued) in the interrupt INTxx servicing. The interrupt request
INTyy is not acknowledged and multiplexed interrupt servicing is not performed. INTyy is held pending and is
acknowledged after INTxx servicing is completed.
IE = 0: Interrupt request acknowledgment disabled.
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CHAPTER 11 INTERRUPT FUNCTIONS
Figure 11-14. Example of Multiplexed Interrupt Servicing
Example 1. Acknowledging multiplexed interrupts
INTxx processing
IE = 0
INTyy
INTxx processing
IE = 0
INTyy
IE = 0
User's Manual U12978EJ3V0UD
IE = 0
EI
RETI
INTyy is held pending
RETI
INTyy processing
RETI
INTyy processing
RETI