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Rev. 1.40
36
March 29, 2019
Rev. 1.40
37
March 29, 2019
HT45F23A/HT45F24A
TinyPower
TM
Flash MCU with OPA & Comparators
HT45F23A/HT45F24A
TinyPower
TM
Flash MCU with OPA & Comparators
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
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. External oscillators requiring some external
components as well as fully integrated internal oscillators, requiring no external components,
are provided to form a wide range of both fast and slow system oscillators. All oscillator options
are selected through the configuration options. The higher frequency oscillators provide higher
performance but carry with it the disadvantage of higher power requirements, while the opposite
is of course true for the lower frequency oscillators. 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.
Type
Name
Freq.
Pins
External Crystal
HXT
400kHz~8MHz
OSC1/OSC2
External RC
ERC
4MHz
OSC1
Internal High Speed RC
HIRC
910kHz, 2/4/8MHz
—
External Clock
EC
400kHz~8MHz
OSC1
External Low Speed Crystal
LXT
32.768kHz
XT1/XT2
Internal Low Speed RC
LIRC
32kHz
—
Oscillator Types
System Clock Configurations
There are six methods of generating the system clock, four high speed oscillators and two low
speed oscillators. The high speed oscillators are the external crystal/ ceramic oscillator, external RC
network oscillator, external clock and the internal 910kHz, 2MHz, 4MHz or 8MHz RC oscillator.
The two low speed oscillators are the internal 32kHz RC oscillator and the external 32.768kHz
crystal oscillator.