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CHAPTER 16 INTERRUPT AND TEST FUNCTIONS
User’s Manual U11302EJ4V0UM
Figure 16-15. Multiple Interrupt Servicing Example (1/2)
Example 1. Two interrupts are generated
During interrupt INTxx servicing, two interrupt requests, INTyy and INTzz are acknowledged, and
multiple interrupt servicing is generated. An EI instruction is issued before each interrupt request
acknowledgment, and the interrupt request acknowledgment enabled state is set.
Example 2. Multiple interrupt servicing is not generated due to priority control
The interrupt request INTyy generated during interrupt INTxx servicing is not acknowledged because
its interrupt priority is lower than that of INTxx, and multiple interrupt servicing is not generated. The
INTyy request is held pending and acknowledged after execution of 1 instruction of the main
processing.
PR = 0: Higher priority level
PR = 1: Lower priority level
IE = 0:
Interrupt request acknowledgment disabled
Main processing
EI
INTxx
(PR = 1)
INTyy
(PR = 0)
IE = 0
EI
RETI
INTxx
servicing
INTzz
(PR = 0)
IE = 0
EI
RETI
INTyy
servicing
IE = 0
RETI
INTzz
servicing
Main processing
INTxx
servicing
INTyy
servicing
INTxx
(PR = 0)
1 instruction
execution
IE = 0
INTyy
(PR = 1)
EI
IE = 0
EI
RETI
RETI