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CHAPTER 8 INTERRUPTS
8.1.3
Nested Interrupts
You can set different interrupt levels for two or more interrupt requests from peripheral
resources in the interrupt level setting registers (ILR0 to ILR5) to process the nested
interrupts.
■
Nested Interrupts
If an interrupt request of higher-priority interrupt level occurs while an interrupt service routine is being
executed, the CPU halts processing of the current interrupt and accepts the higher-priority interrupt request.
The interrupt level can be set to 0 to 3. If it is set to 3, the CPU will accept no interrupt request.
[Example: Nested interrupts]
To assign higher priority to external interrupts over timer interrupts as an example of processing nested-
interrupts, set the timer interrupt and external interrupt levels to 2 and 1, respectively. If an external
interrupt occurs while a timer interrupt is being processed with these settings in use, the interrupts are
processed as shown in Figure 8.1-3.
Figure 8.1-3 Example of Processing Nested Interrupts
•
While a timer interrupt is being processed, the interrupt level bits in the condition code register (CCR:
IL1, IL0) hold the same value as that of the interrupt level setting registers (ILR0 to ILR5)
corresponding to the current timer interrupt (level 2 in this example). If an interrupt request with a
higher-priority interrupt level (level 1 in the example) occurs, the higher-priority interrupt is processed
preferentially.
•
To temporarily disable nested interrupt processing while a timer interrupt is being processed, set the
interrupt enable flag in the condition code register to disable interrupts (CCR:I = 0) or set the interrupt
level bits (CCR: IL1, IL0) to "00
B
".
•
Executing the interrupt return instruction (RETI) after interrupt processing is completed restores the
program counter (PC) and program status (PS) values saved in a stack and resumes the processing of the
interrupted program.
Restoring the program status (PS) also restores the condition code register (CCR) to its value existing
prior to the interrupt.
(6) Process timer interrupt.
(7) Return from timer interrupt.
(3) External interrupt
occurs.
(4)
Process external interrupt.
(5)
Return from external interrupt.
Timer Interrupt Processing
Main Program
External Interrupt Processing
Interrupt level 2
(CCR:IL1,IL0=10
B
)
Initialize peripheral (1)
resources.
Timer interrupt occurs. (2)
Resume main program. (8)
Resume
Interrupt level 1
(CCR:IL1,IL0=01
B
)
Suspend
Содержание F2 MC-8FX Family
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Страница 30: ...16 CHAPTER 1 DESCRIPTION 1 FPT 64P M23 FPT 64P M24 2 For the I O circuit type refer to 1 8 I O Circuit Type ...
Страница 34: ...20 CHAPTER 1 DESCRIPTION ...
Страница 35: ...21 CHAPTER 2 HANDLING DEVICES This chapter gives notes on using 2 1 Device Handling Precautions ...
Страница 38: ...24 CHAPTER 2 HANDLING DEVICES ...
Страница 39: ...25 CHAPTER 3 MEMORY SPACE This chapter describes memory space 3 1 Memory Space 3 2 Memory Map ...
Страница 43: ...29 CHAPTER 4 MEMORY ACCESS MODE This chapter describes the memory access mode 4 1 Memory Access Mode ...
Страница 56: ...42 CHAPTER 5 CPU ...
Страница 73: ...59 CHAPTER 6 CLOCK CONTROLLER ...
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Страница 104: ...90 CHAPTER 7 RESET ...
Страница 105: ...91 CHAPTER 8 INTERRUPTS This chapter explains the interrupts 8 1 Interrupts ...
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Страница 218: ...204 CHAPTER 13 WATCH PRESCALER ...
Страница 257: ...243 CHAPTER 16 8 16 BIT COMPOSITE TIMER ...
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Страница 382: ...368 CHAPTER 21 UART SIO DEDICATED BAUD RATE GENERATOR ...
Страница 390: ...376 CHAPTER 22 I2C ...
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Страница 430: ...416 CHAPTER 23 10 BIT A D CONVERTER ...
Страница 476: ...462 CHAPTER 24 LCD CONTROLLER ...
Страница 482: ...468 CHAPTER 25 LOW VOLTAGE DETECTION RESET CIRCUIT ...
Страница 494: ...480 CHAPTER 26 CLOCK SUPERVISOR ...
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Страница 536: ...522 CHAPTER 28 256 KBIT FLASH MEMORY ...
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Страница 564: ...550 CHAPTER 29 EXAMPLE OF SERIAL PROGRAMMING CONNECTION ...
Страница 595: ...581 INDEX INDEX The index follows on the next page This is listed in alphabetic order ...
Страница 596: ...582 INDEX Index ...
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Страница 599: ...585 Pin Function Index V2 LCD power supply driving pin 2 439 V3 LCD power supply driving pin 3 439 ...
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