HT45R22E Holtek Semiconductor, HT45R22E Datasheet - Page 21

• Manufacturer Part Number: HT45R22E
• Description: Remote Type 8-bit OTP MCU
• Manufacturer: Holtek Semiconductor

Timing Diagram
Note: The write cycle time t
dition of sequential command.
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.
System 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 functions. External oscillators
requiring some external components as well as two fully
integrated internal oscillators, requiring no external
components, are provided to form a wide range of both
fast and slow system oscillators.
Rev. 1.00
External Crystal
External RC
Internal High
Speed RC
External Low
Speed Crystal
Internal Low
Speed RC
Type
Name
HIRC
LIRC
ERC
HXT
LXT
WR
is the time from a valid stop condition of a write sequence to the end of the valid start con-
400kHz~
4MHz
400kHz~
4MHz
4095kHz
32768Hz
10kHz
Freq.
OSC1/
OSC2
OSC1/
OSC2
OSC1
XT2*
Pins
XT1/
21
System Clock Configurations
There are five system oscillators. Three high speed os-
cillators and two low speed oscillators. The high speed
oscillators are the external crystal/ceramic oscillator -
HXT, the external - ERC, and the internal RC oscillator -
HIRC. The two low speed oscillator are the external
32768Hz oscillator - LXT and the internal 10kHz
(V
External Crystal/Resonator Oscillator - HXT
The simple connection of a crystal across OSC1 and
OSC2 will create the necessary phase shift and feed-
back for oscillation. However, for some crystals and
most resonator types, to ensure oscillation and accurate
frequency generation, it is necessary to add two small
value external capacitors, C1 and C2. The exact values
of C1 and C2 should be selected in consultation with the
crystal or resonator manufacturer s specification.
DD
=3V) oscillator - LIRC.
Crystal/Resonator Oscillator - HXT
HT45R22E
March 17, 2010
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