HT68F13 datasheet(28/161 Pages) HOLTEK

28 / 161 page

The actual source clock used for each of the high speed and low speed oscillators is chosen via

configuration options. The frequency 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 selections

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.

ExternalCrystal/CeramicOscillator

- 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.

CrystalOscillatorC1andC2Values

CrystalFrequency

12MHz

0pF

8MHz

0pF

4MHz

0pF

1MHz

100pF

Note:

C1andC2valuesareforguidanceonly.

CrystalRecommendedCapacitorValues

Rev.1.10

February9,2011

HT68F13/HT68F14/HT68F15

EnhancedI/OFlashType MCU

O S C 1

O S C 2

R f

T o i n t e r n a l

c i r c u i t s

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

C 1

C 2

R p

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/ResonatorOscillator

- HXT

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