SN8P1602B
8-Bit Micro-Controller
WAKEUP TIME
OVERVIEW
The external high-speed oscillator needs a delay time from stopping to operating. The delay is necessary for oscillator
to be stabilized.. The delay time for external high-speed oscillator restart is sometimes called wakeup time.
Following are two conditions require wakeup time, one is switching power down mode to normal mode, and the other is
switching slow mode to normal mode. For the first condition, SN8P1602B provides 2048 oscillator clocks as the
wakeup time. The second condition, users need to take the wakeup time into consideration, which involved stabilizing
period for start up the external high-speed oscillator.
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), only the I/O ports with wakeup function are able to 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.
ꢀ
SN8P1602B
0C0H
P1W
Bit 7
0
-
Bit 6
0
-
Bit 5
0
-
Bit 4
P14W
R/W
0
Bit 3
P13W
R/W
0
Bit 2
P12W
R/W
0
Bit 1
P11W
R/W
0
Bit 0
P10W
R/W
0
Read/Write
After reset
-
-
-
P10W~P14W: Port 1 wakeup function control bits. 0 = none wakeup function, 1 = Enable each pin of Port 1 wakeup
function.
SONiX TECHNOLOGY CO., LTD
Page 47
Version 1.1
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