HT68F14 HOLTEK [Holtek Semiconductor Inc], HT68F14 Datasheet - Page 27

• Manufacturer Part Number: HT68F14
• Description: Enhanced I/O Flash Type MCU
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

HT68F13/HT68F14/HT68F15
Enhanced I/O Flash Type MCU
Oscillator
Rev. 1.10
Oscillator Overview
System Clock Configurations
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.
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 device has the flexibility to optimize the performance/ power ratio, a
feature especially important in power sensitive portable applications.
There are four system oscillators, three high speed oscillators and one low speed oscillator. The high
speed oscillators are the external crystal/ceramic oscillator - HXT, the external - ERC, and the internal
RC oscillator - HIRC. The low speed oscillator is the internal 32 kHz oscillator - LIRC. 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.
External Crystal
External RC
Internal High Speed RC
Internal Low Speed RC
High Speed
Low Speed
Oscillator
Oscillator
HIRC
LIRC
ERC
HXT
High Speed Oscillator
Configuration Option
Type
f
LIRC
f
H
System Clock Configurations
6-stage Prescaler
f
H
Oscillator Types
/64
Name
HIRC
LIRC
f
ERC
HXT
H
/32
f
H
/16
27
f
f
f
H
SUB
L
/8
f
400kHz~20MHz
H
CKS2~CKS0 bits
4, 8 or 12MHz
/4
f
H
Fast Wake-up from SLEEP Mode or
/2
IDLE Mode Control (for HXT only)
32kHz
HLCLK,
8MHz
Freq.
OSC1/OSC2
f
SYS
OSC1
Pins
¾
¾
February 9, 2011