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I Return from Sleep Mode
The sleep mode is cancelled by a reset factor or when an interrupt is generated.
G
Return by reset factor
When the sleep mode is cancelled by a reset factor, the mode transits to the main clock mode after the sleep
mode is cancelled, transiting to the reset sequence.
Notes:
• For returning from subsleep mode to main clock mode using the external reset pin (RST
pin), input the Low level for at least oscillator's oscillation time* + 100 µs + 16 machine
cycles (main clock).*:The oscillation time for the oscillator is the period of time taken
until its amplitude reaches 90%.
It takes several to dozens of ms for crystal oscillators, hundreds of µs to several ms for
FAR/ceramic oscillators, and 0 ms for external clocks.
• There is no sub-clock in MB90F897S.
G
Return by interrupt
When a higher interrupt request than the interrupt level (IL) of 7 is generated from the resources in the
sleep mode, the sleep mode is cancelled.After the sleep mode is cancelled, as with normal interrupt
processing, the generated interrupt request is identified according to the settings of the I flag in the
condition code register (CCR), the interrupt level mask register (ILM), and the interrupt control register
(ICR).
• When the CPU is not ready to accept any interrupt request, the next instruction to the currently
executing instruction is executed.
• When the CPU is ready to accept any interrupt request, it branches immediately to the interrupt
processing routine.
Figure 3.8-6 shows the cancellation of sleep mode by an interrupt.
Set to interrupt flag of resources
Note:
When handling an interrupt, the CPU usually services the interrupt after executing the
instruction that follows the one specifying the sleep mode.
Figure 3.8-6 Cancellation of Sleep Mode by Interrupt
NO
INT generate (IL<7)
YES
YES
I = 0
NO
YES
ILM
NO
Execution of interrupt
process
No cancellation of sleep
No cancellation of sleep
Cancellation of sleep
Execute the next instruction
CHAPTER 3 CPU
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