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Rev. 1.00
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Standard 8051 8-Bit Flash MCU
HT85F2260/HT85F2270/HT85F2280
Oscillators
Oscillators
External LXT Oscillator – LXT
32768Hz Crystal Recommended Capacitor Values
LXT Oscillator C1 and C2 Values
Crystal Frequency
C1
C2
3�768Hz
10pF
10pF
Note:
C1 and C� val�es a�e fo� g�idance onl�.
Internal Low Speed RC Oscillator – LIRC
The internal low speed oscillator, LIRC, is a fully self-contained free running on-chip RC
oscillator, used as a clock source for the Watchdog Timer and the Time Base functions. When
the microcontroller enters the IDLE Mode, the CPU clock is switched off to stop microcontroller
activity and to conserve power, however the LIRC oscillator will continue to run and can maintain
WDT and Time Base operation if it is selected as their clock source. The LIRC oscillator has
a typical frequency of 32kHz at 5V and requires no external components, however its actual
frequency may vary with temperature and supply voltage. For precise low speed oscillator
functions the LXT oscillator should be used.