CHAPTER 14 INTERRUPT FUNCTIONS
Figure 14-15. Example of Multiple Interrupts
Example 1. Acknowledging multiple interrupts
INTxx servicing
INTyy servicing
Main servicing
IE = 0
IE = 0
EI
EI
INTxx
INTyy
RETI
RETI
The interrupt request INTyy is acknowledged during the servicing of interrupt INTxx and multiple interrupts are
performed. Before each interrupt request is acknowledged, the EI instruction is issued and the interrupt request is
enabled.
Example 2. Multiple interrupts are not performed because interrupts are disabled
INTxx servicing
INTyy servicing
Main servicing
EI
IE = 0
INTyy is held pending
INTyy
RETI
INTxx
IE = 0
RETI
Because interrupt requests are disabled (the EI instruction has not been issued) in the interrupt INTxx servicing,
the interrupt request INTyy is not acknowledged and multiple interrupts are not performed. INTyy is held pending
and is acknowledged after INTxx servicing is completed.
IE = 0: Interrupt requests disabled
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User’s Manual U15075EJ1V0UM00
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