NEC mPD789426 Series User Manual page 276

Main servicing
INTxx
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
Main servicing
INTxx
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
276
CHAPTER 14 INTERRUPT FUNCTIONS
Figure 14-15. Example of Multiple Interrupts
Example 1. Acknowledging multiple interrupts
IE = 0
EI
INTyy
EI
IE = 0
INTyy
User's Manual U15075EJ1V0UM00
INTxx servicing
IE = 0
EI
RETI
INTxx servicing
RETI
IE = 0
INTyy servicing
RETI
INTyy servicing
INTyy is held pending
RETI