Exte�Nal C�Ystal/Ce�A�Ic Oscillato� - Hxt - Holtek HT66F20-1 Manual

H i g h S p e e d
O s c i l l a t i o n
H X T
E R C
H I R C
H i g h S p e e d O s c i l l a t i o n
C o n f i g u r a t i o n O p t i o n
L o w S p e e d
O s c i l l a t i o n
L I R C
L X T
L o w S p e e d O s c i l l a t i o n
C o n f i g u r a t i o n O p t i o n
External Crystal/Ceramic Oscillator – HXT
The External Crystal/Ceramic System Oscillator is one of the high frequency oscillator choices,
which is selected via configuration option. For most crystal oscillator configurations, the simple
connection of a crystal across OSC1 and OSC2 will create the necessary phase shift and feedback for
oscillation, without requiring external capacitors. However, for some crystal types and frequencies,
to ensure oscillation, it may be necessary 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
thatthe crystal and any associated resistors andcapacitors along with interconnectinglines are all
located as close to the MCUas possible.
Rev. 1.40
HT66F20-1/HT66F30-1/HT68F20-1/HT68F30-1
f
H
6 - s t a g e P r e s c a l e r
f
L
System Clock Configurations
C 1
O S C 1
R p R f
O S C 2
C 2
N o t e : 1 . R p i s n o r m a l l y n o t r e q u i r e d . C 1 a n d C 2 a r e r e q u i r e d .
2 . A l t h o u g h n o t s h o w n O S C 1 / O S C 2 p i n s h a v e a p a r a s i t i c
c a p a c i t a n c e o f a r o u n d 7 p F .
Crystal/Resonator Oscillator – HXT
44
Flash MCU with EEPROM
f / 2
H
f / 4
H
f / 8
H
f / 1 6
H
f / 3 2
H
f / 6 4
H
H L C L K ,
C K S 2 ~ C K S 0 b i t s
f
S U B
F a s t W a k e - u p f r o m S L E E P M o d e o r
I D L E M o d e C o n t r o l ( f o r H X T o n l y )
I n t e r n a l
O s c i l l a t o r
C i r c u i t
T o i n t e r n a l
c i r c u i t s
�ove��e� ��� �01�
f
S Y S