CHAPTER 10 INTERRUPT FUNCTIONS
User's Manual U11919EJ3V0UM00
164
Figure 10-14. Example of Nesting
Example 1. Nesting is accepted
INTyy
EI
Main Processing
EI
INTyy Processing
INTxx Processing
RETI
IE = 0
INTxx
RETI
IE = 0
During interrupt INTxx servicing, interrupt request INTyy is accepted, and a nesting is generated. An EI
instruction is issued before each interrupt request acceptance, and the interrupt request acceptance enable state is
set.
Example 2. A nesting is not generated because interrupts are not enabled
INTyy
EI
Main Processing
RETI
INTyy Processing
INTxx Processing
IE = 0
INTxx
RETI
INTyy is kept pending
IE = 0
Because interrupts are not enabled in interrupt INTxx servicing (an EI instruction is not issued), interrupt request
INTyy is not accepted, and a nesting is not generated. The INTyy request is reserved and accepted after the INTxx
processing is performed.
IE = 0: Interrupt request acceptance disabled
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