SN8P2714X_2715
8-bit micro-controller build-in 12-bit ADC
SONiX TECHNOLOGY CO., LTD
Page 56
V1.4
7.5 WAKEUP TIME
7.5.1 OVERVIEW
The external high-speed oscillator needs a delay time from stopping to operating. The delay is very necessary and
makes the oscillator to work stably. Some conditions during system operating, the external high-speed oscillator often
runs and stops. Under these conditions, the delay time for external high-speed oscillator restart is called wakeup time.
There are two conditions need wakeup time. One is power down mode to normal mode. The other one is slow mode to
normal mode. For the first case, SN8P2710 provides 4096 oscillator clocks to be the wakeup time. However, in the last
case, users need to make the wakeup time by themselves.
7.5.2 HARDWARE WAKEUP
When the system is in power down mode (sleep mode), the external high-speed oscillator stops. For wakeup into
normal, SN8P2710 provides 4096 external high-speed oscillator clocks to be the wakeup time for warming up the
oscillator circuit. After the wakeup time, the system goes into the normal mode. The value of the wakeup time is as
following.
The Wakeup time = 1/Fosc * 3584 (sec) + X’tal settling time
The x’tal settling time is depended on the x’tal type. Typically, it is about 2~4mS.
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Example: In power down mode (sleep mode), the system is waked up by P0 trigger signal. After the wakeup
time, the system goes into normal mode. The wakeup time of P0 wakeup function is as following.
The wakeup time = 1/Fosc * 3584 = 1.001 ms (Fosc = 3.58MHz)
The total wakeup time = 1.001 ms + x’tal settling time
Under power down mode (sleep mode), there are only I/O ports with wakeup function making the system to return
normal mode. Port 0.0 and Port 0.1 wakeup function always enables.
