NEC mPD178054 Series User Manual page 175

Figure 12-13. Multiple Interrupt Servicing Example (2/2)
Example 3. Example where multiple interrupt does not occur because interrupts are not enabled
Main processing
EI
INTxx
(PR = 0)
1 instruction
execution
Because interrupts are not enabled (EI instruction is not issued) in interrupt servicing INTxx, interrupt
request INTyy is not acknowledged, and multiple interrupt does not occur. The INTyy request is held
pending, and is acknowledged after one instruction of the main routine has been executed.
PR = 0: High priority level
IE = 0: Acknowledging interrupts is disabled.
CHAPTER 12 INTERRUPT FUNCTIONS
INTxx INTyy
service service
IE = 0
INTyy
(PR = 0)
RETI
IE = 0
User's Manual U15104EJ2V0UD
RETI
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