HT66F13 datasheet(31/173 Pages) HOLTEK

31 / 173 page

ExternalRCOscillator

- ERC

Using the ERC oscillator only requires that a resistor, with a value between 24k

W and 2.4MW, is

connected between OSC1 and VDD, and a capacitor is connected between OSC1 and ground, providing

a low cost oscillator configuration. It is only the external resistor that determines the oscillation

frequency; the external capacitor has no influence over the frequency and is connected for stability

purposes only. Device trimming during the manufacturing process and the inclusion of internal

frequency compensation circuits are used to ensure that the influence of the power supply voltage,

temperature and process variations on the oscillation frequency are minimised. As a resistance/

frequency reference point, it can be noted that with an external 120k

W resistor connected and with a

5V voltage power supply and temperature of 25

°C degrees, the oscillator will have a frequency of

8MHz within a tolerance of 2%. Here only the OSC1 pin is used, which is shared with I/O pin PB1,

leaving pin PB2 free for use as a normal I/O pin.

InternalRCOscillator

- HIRC

The internal RC oscillator is a fully integrated system oscillator requiring no external components. The

internal RC oscillator has three fixed frequencies of either 4MHz, 8MHz or 12MHz. Device trimming

during the manufacturing process and the inclusion of internal frequency compensation circuits are

used to ensure that the influence of the power supply voltage, temperature and process variations on

the oscillation frequency are minimised. As a result, at a power supply of either 3V or 5V and at a

temperature of 25

°C degrees, the fixed oscillation frequency of 4MHz, 8MHz or 12MHz will have a

tolerance within 2%. Note that if this internal system clock option is selected, as it requires no external

pins for its operation, I/O pins PB1 and PB2 are free for use as normal I/O pins.

Internal32kHzOscillator

- LIRC

The Internal 32kHz System Oscillator is one of the low frequency oscillator choices, which is selected

via configuration option. It is a fully integrated RC oscillator with a typical frequency of 32kHz at 5V,

requiring no external components for its implementation. Device trimming during the manufacturing

process and the inclusion of internal frequency compensation circuits are used to ensure that the

influence of the power supply 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¢J degrees, the fixed

oscillation frequency of 32kHz will have a tolerance within 10%.

SupplementaryOscillator

The low speed oscillator, in addition to providing a system clock source, is also used to provide a clock

source to two other device functions. These are the Watchdog Timer and the Time Base Interrupts.

Rev.1.10

February9,2011

HT66F13/HT66F14/HT66F15

EnhancedA/DFlashType MCU

O S C 1

2 0 p F

V D D

R O S C

P B 2

ExternalRCOscillator

- ERC

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