HT46R0664 datasheet(28/92 Pages) HOLTEK

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HT46R0664

Enhanced A/D+LCD Type 8-Bit OTP MCU

External RC Oscillator – ERC

Using the ERC oscillator only requires that a resistor, with a value between 24kΩ and 1.5MΩ,

is connected between OSC1 and VDD, and a capacitor is connected between OSC 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. Here only

the OSC1 pin is used and leaving OSC2 as a general I/O Port.

PA6 /O SC 1

470pF

V DD

R OS C

PA5 /O SC 2

External RC Oscillator – ERC

Internal RC Oscillator – 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. Note that if this internal system clock option

is selected, as it requires no external pins for its operation.

Internal RC

Oscillator

PA5/OSC2

PA6/OSC1

Internal RC Oscillator – HIRC

External 32768Hz Crystal Oscillator – LXT

When the microcontroller enters the Idle/Sleep Mode, the system clock is switched off to stop

microcontroller activity and to conserve power. However, in many microcontroller applications it

may be necessary to keep the internal timers operational even when the microcontroller is in the

Power-down Mode. To do this, another clock, independent of the system clock, must be provided.

To do this a configuration option exists to allow a high speed oscillator to be used in conjunction

with a low speed oscillator, known as the LXT oscillator. The LXT oscillator is implemented using

a 32768Hz crystal connected to pins XT1/XT2. However, for some crystals, to ensure oscillation

and accurate frequency generation, it is necessary to add two small value external capacitors, C1 and

C2. The exact values of C1 and C2 should be selected in consultation with the crystal or resonator

manufacturer’s specification. The external parallel feedback resistor, Rp, is required. The LXT

oscillator must be used together with the HXT, ERC or HIRC register.

HT46R0664 Datasheet(PDF) 28 Page - Holtek Semiconductor Inc

HT46R0664 Datasheet(HTML) 28 Page - Holtek Semiconductor Inc

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