SN8P1600
8-bit micro-controller
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 work stably. The external high-speed oscillator sometimes starts and stops at different situations.
The delay time for external high-speed oscillator restart is called Wakeup time.
Following are two conditions need Wakeup time. One is switching power down mode to normal mode. The other is
switching slow mode to normal mode. For the first case, SN8P1600 provides 2048 oscillator clocks as the Wakeup
time. The second case, users need to calculate the Wakeup time.
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.
ꢃ
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.
ꢂ
SN8P1602/1603
0C0H
P1W
Bit 7
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
0
-
-
Read/Write
After reset
-
-
ꢂ
SN8P1604
0C0H
P1W
Bit 7
P17W
R/W
0
Bit 6
P16W
R/W
0
Bit 5
P15W
R/W
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 Wakeup function.
SONiX TECHNOLOGY CO., LTD
Page 50
Revision 1.94
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