HT83F10 HOLTEK [Holtek Semiconductor Inc], HT83F10 Datasheet - Page 39

• Manufacturer Part Number: HT83F10
• Description: Flash Type Voice OTP MCU
• Manufacturer: HOLTEK [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
The simple connection of a crystal across OSC1 and
OSC2 will create the necessary phase shift and feed-
back for oscillation, and will normally not require exter-
nal capacitors. However, for some crystals and most
resonator types, to ensure oscillation and accurate fre-
quency generation, it may be 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 specifica-
tion. The external parallel feedback resistor, Rp, is nor-
mally not required but in some cases may be needed to
assist with oscillation start up.
Rev. 1.00
External crystal/resonator oscillator
External
Internal Ca, Cb, Rf Typical Values @ 5V, 25°C
11~13pF
Oscillator Internal Component Values
Ca
RC oscillator
Crystal/Resonator Oscillator
13~15pF
Cb
800k
Rf
39
External RC Oscillator
Using the external system RC oscillator requires that a
resistor, with a value between 150k and 300k , is con-
nected between OSC1 and VSS. The generated system
clock divided by 4 will be provided on OSC2 as an out-
put which can be used for external synchronization pur-
poses. Note that as the OSC2 output is an NMOS
open-drain type, a pull high resistor should be con-
nected if it to be used to monitor the internal frequency.
Although this is a cost effective oscillator configuration,
the oscillation frequency can vary with VDD, tempera-
ture and process variations and is therefore not suitable
for applications where timing is critical or where accu-
rate oscillator frequencies are required. For the value of
the external resistor R
typical RC Oscillator vs. Temperature and VDD charac-
teristics 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.
External RC Oscillator
OSC
refer to the Holtek website for
HT83FXX
May 12, 2009