UPD78F9234MC-5A4-A Datasheet, PDF (238/419 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

CHAPTER 13 INTERRUPT FUNCTIONS
Figure 13-10. Example of Multiple Interrupts (1/2)
Example 1. Multiple interrupts are acknowledged
Main processing
INTxx servicing
INTyy servicing
IE = 0
EI
IE = 0
EI
INTxx
INTyy
RETI
RETI
During interrupt INTxx servicing, interrupt request INTyy is acknowledged, and multiple interrupts are generated.
Before each interrupt request acknowledgment, the EI instruction is issued, the interrupt mask is released, and the
interrupt request acknowledgment 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
INTxx servicing
INTyy servicing
EI
INTxx
IE = 0
INTyy
RETI
INTyy is held pending
IE = 0
RETI
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
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User’s Manual U17446EJ5V0UD