HT66F03 View Datasheet(PDF) - Holtek Semiconductor
Part Name
Description
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HT66F03 Datasheet PDF : 139 Pages
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HT66F03/HT66F04/HT68F03/HT68F04
Oscillator
Various oscillator options offer the user a wide range of
functions according to their various application require-
ments. 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 Watch-
dog Timer and Time Base Interrupts. External oscilla-
tors 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 re-
quirements, while the opposite is of course true for the
lower frequency oscillators. With the capability of dy-
namically switching between fast and slow system
clock, the device has the flexibility to optimize the perfor-
mance/power ratio, a feature especially important in
power sensitive portable applications.
Type
Name
Freq.
Pins
External Crystal HXT
400kHz~
20MHz
OSC1/
OSC2
External RC
ERC
8MHz
OSC1
Internal High
Speed RC
HIRC 4, 8 or 12MHz ¾
External Low
Speed Crystal
LXT
32.768kHz
XT1/
XT2
Internal Low
Speed RC
LIRC
32kHz
¾
Oscillator Types
System Clock Configurations
There are five methods of generating the system clock,
three high speed oscillators and two low speed oscilla-
tors. The high speed oscillators are the external crystal/
ceramic oscillator, external RC network oscillator and
the internal 4MHz, 8MHz or 12MHz RC oscillator. The
two low speed oscillators are the internal 32kHz RC os-
cillator and the external 32.768kHz crystal oscillator. Se-
lecting 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.
High Speed Oscillation
HXT
ERC
fH
6-stage Prescaler
HIRC
High Speed Oscillation
Configuration Option
Low Speed Oscillation
fH/2
fH/4
fH/8
fH/16
fH/32
LIRC
fH/64
fL
LXT
Low Speed Oscillation
Configuration Option
fS UB
HLCLK,
CKS2~CKS0 bits
fSY S
Fast Wake-up from SLEEP Mode or
IDLE Mode Control (for HXT only)
System Clock Configurations
Rev. 1.00
27
April 16, 2010
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