HT68F14 HOLTEK [Holtek Semiconductor Inc], HT68F14 Datasheet - Page 28

• Manufacturer Part Number: HT68F14
• Description: Enhanced I/O Flash Type MCU
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

Rev. 1.10
External Crystal/ Ceramic Oscillator - HXT
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.
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.
12MHz
8MHz
4MHz
1MHz
Note: C1 and C2 values are for guidance only.
Crystal Frequency
Crystal Recommended Capacitor Values
Crystal Oscillator C1 and C2 Values
Crystal/Resonator Oscillator - HXT
28
100pF
Enhanced I/O Flash Type MCU
0pF
0pF
0pF
C1
HT68F13/HT68F14/HT68F15
100pF
0pF
0pF
0pF
C2
February 9, 2011