Rev. 1.71
36
April 11, 2017
Rev. 1.71
37
April 11, 2017
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
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 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, these devices
have the flexibility to optimize the performance/power ratio, a feature especially important in power
sensitive portable applications.
Type
Name
Freq.
Internal High Speed RC
HIRC
8MHz
Internal Low Speed RC
LIRC
32kHz
Oscillator Types
System Clock Configurations
There are two methods of generating the system clock, a high speed oscillator and a low speed
oscillator. The high speed oscillator is the internal
8MHz
RC oscillator. The low speed oscillator is
the internal 32kHz RC oscillator. 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
and as the system clock can be dynamically selected.
HIRC
Prescaler
f
H
LIRC
Low Speed Oscillation
f
H
/2
f
H
/16
f
H
/64
f
H
/8
f
H
/4
f
H
/32
HLCLK
CKS2~CKS0 bits
f
SYS
f
L
High Speed Oscillation
System Clock Configurations