ht82j30r Holtek Semiconductor Inc., ht82j30r Datasheet - Page 26

• Manufacturer Part Number: ht82j30r
• Description: Ht82j30r/ht82j30a -- 16 Channel A/d Mcu With Spi Interface
• Manufacturer: Holtek Semiconductor Inc.

Oscillator
Various oscillator options offer the user a wide range of
functions according to their various application require-
ments. Two types of system clocks can be selected
while various clock source options for the Watchdog
Timer are provided for maximum flexibility. All oscillator
options are selected through the configuration options.
The two methods of generating the system clock are:
One of these two methods must be selected using the
configuration options.
More information regarding the oscillator is located in
Application Note HA0075E on the Holtek website.
External Crystal/Resonator Oscillator
After selecting the correct configuration option, for most
crystal oscillator configurations, the simple connection
of a crystal across OSC1 and OSC2 will create the nec-
essary phase shift and feedback for oscillation. How-
ever, to ensure oscillation, it is recommended that two
small value capacitors and a resistor, the values of
which are shown in the table, should be connected as
shown in the diagram.
The following table shows the C1, C2 and R1 values ac-
cording different crystal values.
Note:
Rev. 1.10
4MHz Crystal
4MHz Resonator (3 pins)
4MHz Resonator (2 pins)
3.58MHz Crystal
3.58MHz Resonator (2 pins)
2MHz Crystal & Resonator (2 pins)
1MHz Crystal
480kHz Resonator
455kHz Resonator
429kHz Resonator
External crystal/resonator oscillator
External RC oscillator
Crystal or Resonator
The resistance and capacitance for reset circuit
should be designed in such a way as to ensure
Crystal/Ceramic Oscillator
C1, C2
300pF
300pF
300pF
10pF
25pF
25pF
35pF
0pF
0pF
0pF
9.1k
10k
12k
12k
10k
10k
10k
27k
10k
10k
R1
26
External RC Oscillator
Using the external system RC oscillator requires that a
resistor, with a value between 4.7k and 750k , is con-
nected between OSC1 and VDD, and a capacitor is con-
nected to ground. The generated system clock divided by
4 will be provided on OSC2 as an output which can be
used for external synchronization purposes. Note that as
the OSC2 output is an NMOS open-drain type, a pull high
resistor should be connected if it to be used to monitor the
internal frequency. Although this is a cost effective oscil-
lator configuration, the oscillation frequency can vary with
VDD, temperature and process variations and is there-
fore not suitable for applications where timing is critical or
where accurate oscillator frequencies are required.For
the value of the external resistor R
website for typical RC Oscillator vs. Temperature and
VDD characteristics graphics. Note that it is the only
microcontroller internal circuitry together with the external
resistor, that determine the frequency of the oscillator.
The external capacitor shown on the diagram does not
influence the frequency of oscillation.
Watchdog Timer Oscillator
The WDT oscillator is a fully self-contained free running
on-chip RC oscillator with a typical period of 65 s at 5V
requiring no external components. When the device en-
ters the Power Down Mode, the system clock will stop
running but the WDT oscillator continues to free-run and
to keep the watchdog active. However, to preserve
power in certain applications the WDT oscillator can be
disabled via a configuration option.
that the V
operating voltage range before bringing RES to
high.
nected to the RES pin as short as possible, to
avoid noise interface.
* Make the length of the wiring, which is con-
DD
RC Oscillator
is stable and remains within a valid
HT82J30R/HT82J30A
OSC
refer to the Holtek
March 13, 2008