Oscillator
Various oscillator options 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 registers.
Oscillator Overview
The devices include two internal oscillators, a low speed oscillator and high speed oscillator. Both can
be chosen as the clock source for the main system clock however the slow speed oscillator is also used
as a clock source for other functions such as the Watchdog Timer, Time Base and Timer/Event
Counter. Both oscillators require no external components for their implementation. All oscillator
options are selected using registers. The high speed oscillator provides higher performance but carries
with it the disadvantage of higher power requirements, while the opposite is of course true for the low
speed oscillator. With the capability of dynamically switching between fast and slow system clock,
the device has the flexibility to optimise the performance/power ratio, a feature especially important
in power sensitive portable applications.
Type
Name
Freq.
Internal High Speed
HIRC
8, 12 or 16MHz
Internal Low Speed
LIRC
32kHz
Oscillator Types
System Clock Configurations
There are two methods of generating the system clock, a high speed internal clock source and low
speed internal clock source. The high speed oscillator is an internal 8MHz, 12MHz or 16MHz RC
oscillator while the low speed oscillator is an internal 32kHz RC oscillator. Both oscillators are fully
integrated and do not require external components. Selecting whether the low or high speed oscillator
is used as the system oscillator is implemented using the HLCLK bit and CKS2 ~ CKS0 bits in the
SMOD register allowing the system clock to be dynamically selected.
Internal High Speed RC Oscillator
-
HIRC
The internal High Speed RC oscillator is a fully integrated system oscillator requiring no external
components. The internal RC oscillator has a power on default frequency of 8 MHz but can be selected
to be either 8MHz, 12MHz or 16MHz using the HIRCS1 and HIRCS0 bits in the CTRL register.
Device trimming during the manufacturing process and the inclusion of internal frequency
compensation circuits are used to ensure that the influence of the power supply voltage, temperature
and process variations on the oscillation frequency are minimised.
Rev. 1.50
36
April 28, 2020
BS83B08-3/B12-3/B16-3/B16G-3/C24-3
8-Bit Touch Key Flash MCU