SN8P2740 Series
ADC, OP-amp, Comparator 8-Bit Micro-Controller
5.7 WAKEUP
5.7.1 OVERVIEW
Under power down mode (sleep mode) or green mode, program doesn‟t execute. The wakeup trigger can wake the
system up to normal mode or slow mode. The wakeup trigger sources are external trigger (P0/P1 level change) and
internal trigger (T0 timer overflow). The wakeup function builds in interrupt operation issued IRQ flag and trigger
system executing interrupt service routine as system wakeup occurrence.
Power down mode is waked up to normal mode. The wakeup trigger is only external trigger (P0/P1 level change)
Green mode is waked up to last mode (normal mode or slow mode). The wakeup triggers are external trigger
(P0/P1 level change) and internal trigger (T0 timer overflow).
Wakeup interrupt function issues WAKEIRQ as system wakeup from power down mode or green mode. If
WAKEIEN is “1” meaning enable, the wakeup event triggers program counter point to interrupt vector (ORG 8)
executing interrupt service routine.
Note: If wake-up source is external interrupt source, the WAKE bit won’t be set, and external interrupt
IRQ bit is set. The system issues external interrupt request and executes interrupt service routine.
5.7.2 WAKEUP TIME
When the system is in power down mode (sleep mode), the high clock oscillator stops. When waked up from power
down mode, MCU waits for 2048 external high-speed oscillator clocks and 32 internal high-speed oscillator clocks as
the wakeup time to stable the oscillator circuit. After the wakeup time, the system goes into the normal mode.
Note: Wakeup from green mode is no wakeup time because the clock doesn’t stop in green mode.
The value of the external high clock oscillator wakeup time is as the following.
The Wakeup time = 1/Fosc * 2048 (sec) + high clock start-up time
Example: In power down mode (sleep mode), the system is waked up. After the wakeup time, the system
goes into normal mode. The wakeup time is as the following.
The wakeup time = 1/Fosc * 2048 = 0.512 ms (Fosc = 4MHz)
The total wakeup time = 0.512 ms + oscillator start-up time
The value of the internal high clock oscillator RC type wakeup time is as the following.
The Wakeup time = 1/Fosc * 32 (sec) + high clock start-up time
Example: In power down mode (sleep mode), the system is waked up. After the wakeup time, the system
goes into normal mode. The wakeup time is as the following.
The wakeup time = 1/Fosc * 32 = 2 us
(Fhosc = 16MHz)
Note: The high clock start-up time is depended on the VDD and oscillator type of high clock.
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