HT48R063B/064B/065B/066B
Wake-up Function Register - PAWK
HXT, the external - ERC, and the internal RC oscillator -
HIRC. The two low speed oscillator are the external
32768Hz oscillator - LXT and the internal 13kHz
(VDD=5V) oscillator - LIRC.
When the microcontroller enters the Idle/Sleep Mode,
various methods exist to wake the device up and con-
tinue with normal operation. One method is to allow a
falling edge on the I/O pins to have a wake-up function.
This register is used to select which Port A I/O pins are
used to have this wake-up function.
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.
Pull-high Registers -
PAPU, PBPU, PCPU, PDPU, PEPU, PFPU
The I/O pins, if configured as inputs, can have internal
pull-high resistors connected, which eliminates the need
for external pull-high resistors. This register selects which
I/O pins are connected to internal pull-high resistors.
Software COM Register - SCOMC
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The pins PB0~PB3 on Port B can be used as SCOM
lines to drive an external LCD panel. To implement this
function, the SCOMC register is used to setup the cor-
rect bias voltages on these pins.
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Oscillator
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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.
2
.
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Crystal/Resonator Oscillator - HXT
Crystal Oscillator C1 and C2 Values
Crystal Frequency
12MHz
C1
8pF
C2
10pF
10pF
10pF
System Oscillator Overview
8MHz
8pF
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 a two
fully integrated internal oscillators, requiring no external
components, are provided to form a wide range of both
fast and slow system oscillators.
4MHz
8pF
1MHz
100pF
100pF
Note: C1 and C2 values are for guidance only.
Crystal Recommended Capacitor Values
External RC Oscillator - ERC
Type
Name
Freq.
Pins
Using the ERC oscillator only requires that a resistor,
with a value between 24kW and 1.5MW, is connected
between OSC1 and VDD, and a capacitor is connected
between OSC and ground, providing a low cost oscilla-
tor configuration. It is only the external resistor that de-
termines the oscillation frequency; the external
capacitor has no influence over the frequency and is
connected for stability purposes only. Device trimming
during the manufacturing process and the inclusion of
internal frequency compensation circuits are used to en-
sure that the influence of the power supply voltage, tem-
perature and process variations on the oscillation
frequency are minimised. As a resistance/frequency ref-
erence point, it can be noted that with an external 120K
resistor connected and with a 5V voltage power supply
and temperature of 25 degrees, the oscillator will have a
400kHz~
12MHz
OSC1/
OSC2
External Crystal
HXT
400kHz~
12MHz
External RC
ERC
OSC1
Internal High
Speed RC
HIRC 4, 8 or 12MHz
¾
External Low
Speed Crystal
OSC1/
OSC2
LXT
32768Hz
13kHz
Internal Low
Speed RC
LIRC
¾
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 -
Rev. 1.00
25
April 7, 2011
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
