SN8F2280 Series
USB 2.0 Full-Speed 8-Bit Micro-Controller
4.2 SYSTEM LOW CLOCK
The system low clock source is the internal low-speed oscillator built in the micro-controller. The low-speed oscillator
uses RC type oscillator circuit. The frequency is affected by the voltage and temperature of the system. In common
condition, the frequency of the RC oscillator is about 12KHz.
The internal low RC supports watchdog clock source and system slow mode controlled by CLKMD.
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Flosc = Internal low RC oscillator (12KHz).
Slow mode Fcpu = Flosc / N. N = 2 or 4 set by code option.
There are two conditions to stop internal low RC. One is power down mode, and the other is green mode of 12K mode
and watchdog disable. If system is in 12K mode and watchdog disable, only 12K oscillator actives and system is under
low power consumption.
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Example: Stop internal low-speed oscillator by power down mode.
B0BSET
FCPUM0
; To stop external high-speed oscillator and internal low-speed
; oscillator called power down mode (sleep mode).
Note: The internal low-speed clock can’t be turned off individually. It is controlled by CPUM0, CPUM1
(12K, watchdog disable) bits of OSCM register.
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