Preliminary
SN8P1702A/SN8P1703A
8-bit micro-controller build-in 12-bit ADC
WAKEUP TIME
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, SN8P1702A/SN8P1703A provides 2048 oscillator clocks to be the wakeup time. But in
the last case, users need to make the wakeup time by themselves.
HARDWARE WAKEUP
When the system is in power down mode (sleep mode), the external high-speed oscillator stops. When waked up from
power down mode, MCU waits for 2048 external high-speed oscillator clocks as the wakeup time to stable the oscillator
circuit. After the wakeup time, the system goes into the normal mode. The value of the wakeup time is as the following.
The Wakeup time = 1/Fosc * 2048 (sec) + X’tal settling time
The x’tal settling time is depended on the x’tal type. Typically, it is about 2~4mS.
ꢁ
Example: In power down mode (sleep mode), the system is waked up by P0 or P1 trigger signal. After the
wakeup time, the system goes into normal mode. The wakeup time of P0, P1 wakeup function is
as the following.
The wakeup time = 1/Fosc * 2048 = 0.57 ms
(Fosc = 3.58MHz)
The total wakeup time = 0.57ms + x’tal settling time
Under power down mode (sleep mode), there are only I/O ports with wakeup function wake the system up to normal
mode. The Port 0 and Port 1 have wakeup function. Port 0 wakeup function always enables, but the Port 1 is controlled
by the P1W register.
P1W initial value = xxxx xx00
0C0H
P1W
Bit 7
0
-
Bit 6
0
-
Bit 5
0
-
Bit 4
0
-
Bit 3
0
-
Bit 2
0
-
Bit 1
P11W
W
Bit 0
P10W
W
Bit[1:0]
P11W,P10W:Port 1 wakeup function control bits.
0 = Disable each pin of Port1 wakeup function,
1 = Enable each pin of Port 1 wakeup function
SONiX TECHNOLOGY CO., LTD
Page 51
Revision 0.5
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