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Rev. 1.10
34
March 02, 2020
Rev. 1.10
35
March 02, 2020
BS83A02L/BS83B04L
Ultra-Low Power Touch Key Flash MCU
BS83A02L/BS83B04L
Ultra-Low Power Touch Key Flash MCU
Oscillators
Various oscillator types offer the user a wide range of functions according to their various application
requirements. The flexible features of the oscillator functions ensure that the best optimisation can
be achieved in terms of speed and power saving. Oscillator selections and operation are selected
through a combination of configuration options and relevant control registers.
Oscillator Overview
In addition to being the source of the main system clock the oscillators also provide clock sources
for the Watchdog Timer and Time Base Interrupts. Two fully integrated internal oscillators, requiring
no external components, are provided to form a wide range of both fast and slow system oscillators.
The higher frequency oscillator provides higher performance but carry with it the disadvantage of
higher power requirements, while the opposite is of course true for the lower frequency oscillator.
With the capability of dynamically switching between fast and slow system clock, the devices have
the flexibility to optimize the performance/power ratio, a feature especially important in power
sensitive portable applications.
Device
Type
Name
Frequency
BS83A02L
Internal High Speed RC
HIRC
8MHz
Internal Low Speed RC
LIRC
2kHz
BS83B04L
Internal High Speed RC
HIRC
2/4/8MHz
Internal Low Speed RC
LIRC
2kHz
Oscillator Types
System Clock Configurations
There are two methods of generating the system clock, one high speed oscillator and one low speed
oscillator. For the BS83A02L, the high speed oscillator is the internal 8MHz RC oscillator, HIRC.
For the BS83B04L, the high speed oscillator is the internal 2/4/8MHz RC oscillator. The low
speed oscillator is the internal 2kHz RC oscillator, LIRC. Selecting whether the low or high speed
oscillator is used as the system oscillator is implemented using the CKS2~CKS0 bits in the SCC
register and as the system clock can be dynamically selected.
The frequency of the slow speed or high speed system clock is determined using the CKS2~CKS0
bits in the SCC register. Note that two oscillator selections must be made namely one high speed and
one low speed system oscillator. It is not possible to choose a no-oscillator selection for either the
high or low speed oscillator.