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RL78/G1P
CHAPTER 15 INTERRUPT FUNCTIONS
R01UH0895EJ0100 Rev.1.00
589
Nov 29, 2019
Figure 15-10. Examples of Multiple Interrupt Servicing (1/2)
Example 1. Multiple interrupt servicing occurs twice
Main processing
INTxx servicing
INTyy servicing
INTzz servicing
EI
EI
EI
RETI
RETI
RETI
INTxx
(PR = 11)
INTyy
(PR = 10)
INTzz
(PR = 01)
IE = 0
IE = 0
IE = 0
IE = 1
IE = 1
IE = 1
During servicing of interrupt INTxx, two interrupt requests, INTyy and INTzz, are acknowledged, and multiple interrupt
servicing takes place. Before each interrupt request is acknowledged, the EI instruction must always be issued to enable
interrupt request acknowledgment.
Example 2. Multiple interrupt servicing does not occur due to priority control
Main processing
INTxx servicing
INTyy servicing
INTxx
(PR = 10)
INTyy
(PR = 11)
EI
RETI
IE = 0
IE = 0
EI
1 instruction execution
RETI
IE = 1
IE = 1
Interrupt request INTyy issued during servicing of interrupt INTxx is not acknowledged because its priority is lower than
that of INTxx, and multiple interrupt servicing does not take place. The INTyy interrupt request is held pending, and is
acknowledged following execution of one main processing instruction.
PR = 00: Specify level 0 with
PR1
= 0,
PR0
= 0 (higher priority level)
PR = 01: Specify level 1 with
PR1
= 0,
PR0
= 1
PR = 10: Specify level 2 with
PR1
= 1,
PR0
= 0
PR = 11: Specify level 3 with
PR1
= 1,
PR0
= 1 (lower priority level)
IE = 0:
Interrupt request acknowledgment is disabled
IE = 1:
Interrupt request acknowledgment is enabled.