SN8F2270B Series
USB 2.0 Low-Speed 8-Bit Micro-Controller
5.2 SYSTEM MODE SWITCHING EXAMPLE
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Example: Switch normal/slow mode to power down (sleep) mode.
B0BSET FCPUM0 ; Set CPUM0 = 1.
Note: During the sleep, only the wakeup pin and reset can wakeup the system back to the normal mode.
Example: Switch normal mode to slow mode.
B0BSET
B0BSET
FCLKMD
FSTPHX
;To set CLKMD = 1, Change the system into slow mode
;To stop external high-speed oscillator for power saving.
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Example: Switch slow mode to normal mode (The external high-speed oscillator is still running).
B0BCLR FCLKMD ;To set CLKMD = 0
Example: Switch slow mode to normal mode (The external high-speed oscillator stops).
If external high clock stop and program want to switch back normal mode. It is necessary to delay at least 10mS for
external clock stable.
B0BCLR
FSTPHX
; Turn on the external high-speed oscillator.
; internal RC=24KHz (typical) will delay
MOV
A, #20
Z, A
Z
B0MOV
DECMS
JMP
@@:
; 0.33ms X 30 ~ 10ms for external clock stable
@B
;
B0BCLR
FCLKMD
; Change the system back to the normal mode
Example: Switch normal/slow mode to green mode.
B0BSET FCPUM1
; Set CPUM1 = 1.
Note: If T0 timer wakeup function is disabled in the green mode, only the wakeup pin and reset pin can
wakeup the system backs to the previous operation mode.
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Version 1.2
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