354CHAPTER 16 INTERRUPT AND TEST FUNCTIONSUser’s Manual U11302EJ4V0UMFigure 16-15. Multiple Interrupt Servicing Example (1/2)Example 1. Two interrupts are generatedDuring interrupt INTxx servicing, two interrupt requests, INTyy and INTzz are acknowledged, andmultiple interrupt servicing is generated. An EI instruction is issued before each interrupt requestacknowledgment, and the interrupt request acknowledgment enabled state is set.Example 2. Multiple interrupt servicing is not generated due to priority controlThe interrupt request INTyy generated during interrupt INTxx servicing is not acknowledged becauseits interrupt priority is lower than that of INTxx, and multiple interrupt servicing is not generated. TheINTyy request is held pending and acknowledged after execution of 1 instruction of the mainprocessing.PR = 0: Higher priority levelPR = 1: Lower priority levelIE = 0: Interrupt request acknowledgment disabledMain processingEIINTxx(PR = 1)INTyy(PR = 0)IE = 0EIRETIINTxxservicingINTzz(PR = 0)IE = 0EIRETIINTyyservicingIE = 0RETIINTzzservicingMain processing INTxxservicingINTyyservicingINTxx(PR = 0)1 instructionexecution IE = 0INTyy(PR = 1)EI IE = 0EIRETIRETI
