HT66F016 View Datasheet(PDF) - Holtek Semiconductor
Part Name
Description
MFG CO.
'HT66F016' PDF : 116 Pages View PDF
HT66F016/HT66F017/HT68F016/HT68F017
HT66F016R/HT66F017R/HT68F016R/HT68F017R
The actual source clock used for each of the high speed
oscillator is chosen via configuration options. The fre-
quency of the slow speed or high speed system clock is
also determined using the HLCLK bit and CKS2~CKS0
bits in the SMOD register. Note that two oscillator selec-
tions must be made namely one high speed and one low
speed system oscillators. It is not possible to choose a
no-oscillator selection for either the high or low speed
oscillator. The OSC1 and OSC2 pins are used to con-
nect the external components for the external crystal.
External Crystal/Ceramic Oscillator - HXT
The External Crystal/ Ceramic System Oscillator is one
of the high frequency oscillator choices, which is se-
lected via configuration option. For most crystal oscilla-
tor configurations, the simple connection of a crystal
across OSC1 and OSC2 will create the necessary
phase shift and feedback for oscillation, without requir-
ing external capacitors. However, for some crystal types
and frequencies, to ensure oscillation, it may be neces-
sary to add two small value capacitors, C1 and C2.
Using a ceramic resonator will usually require two small
value capacitors, C1 and C2, to be connected as shown
for oscillation to occur. The values of C1 and C2 should
be selected in consultation with the crystal or resonator
manufacturer¢s specification.
For oscillator stability and to minimise the effects of
noise and crosstalk, it is important to ensure that the
crystal and any associated resistors and capacitors
along with inter connecting lines are all located as close
to the MCU as possible.
C1
O SC1
In te r n a l
O s c illa to r
C ir c u it
Rp
Rf
T o in te r n a l
C2
O SC2
c ir c u its
N o te : 1 . R p is n o r m a lly n o t r e q u ir e d . C 1 a n d C 2 a r e r e q u ir e d .
2 . A lth o u g h n o t s h o w n O S C 1 /O S C 2 p in s h a v e a p a r a s itic
c a p a c ita n c e o f a r o u n d 7 p F .
Crystal/Resonator Oscillator - HXT
Crystal Oscillator C1 and C2 Values
Crystal Frequency
C1
C2
12MHz
0pF
0pF
8MHz
0pF
0pF
4MHz
0pF
0pF
1MHz
100pF
100pF
Note: C1 and C2 values are for guidance only.
Crystal Recommended Capacitor Values
Internal RC Oscillator - HIRC
The internal RC oscillator is a fully integrated system os-
cillator requiring no external components. The internal
RC oscillator has a fixed frequency of 8MHz. Device
trimming during the manufacturing process and the in-
clusion of internal frequency compensation circuits are
used to ensure that the influence of the power supply
voltage, temperature and process variations on the os-
cillation frequency are minimised. As a result, at a power
supply of 5V and at a temperature of -40°C ~85°C de-
grees, the fixed oscillation frequency of the high speed
internal 8MHz RC oscillator will have a tolerance within
2%. Note that if this internal system clock option is se-
lected as the high speed oscillator, as it requires no ex-
ternal pins for its operation, I/O pins PA6 and PA5 can
only be used as normal I/O pins.
Internal 32kHz Oscillator - LIRC
The Internal 32kHz System Oscillator is the low fre-
quency oscillator. It is a fully integrated RC oscillator
with a typical frequency of 32kHz at 5V, requiring no ex-
ternal components for its implementation. Device trim-
ming during the manufacturing process and the
inclusion of internal frequency compensation circuits
are used to ensure that the influence of the power sup-
ply voltage, temperature and process variations on the
oscillation frequency are minimised. As a result, at a
power supply of 5V and at a temperature of 25°C de-
grees, the fixed oscillation frequency of 32kHz will have
a tolerance within 10%.
Supplementary Oscillators
The low speed oscillators, in addition to providing a sys-
tem clock source are also used to provide a clock
source to two other device functions. These are the
Watchdog Timer and the Time Base Interrupts.
Rev. 1.40
31
November 22, 2016
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