HT67F60 datasheet(57/242 Pages) HOLTEK

57 / 242 page

HT67F30/HT67F40/HT67F50/HT67F60

TinyPowerTM A/D Flash Type 8-Bit MCU with LCD & EEPROM

Rev. 1.50

March 06 , 2012

Rev. 1.50

March 06 , 2012

LXT Oscillator C1 and C2 Values

Crystal Frequency

32.768kHz

10pF

Note:1. C1 and C2 values are for guidance only.

2. RP=5M~10MΩ is recommended.

32.768kHz Crystal Recommended Capacitor Values

LXT Oscillator Low Power Function

The LXT oscillator can function in one of two modes, the Quick Start Mode and the Low Power

Mode. The mode selection is executed using the LXTLP bit in the TBC register.

LXTLP Bit

LXT Mode

Quick Start

Low-power

After power on the LXTLP bit will be automatically cleared to zero ensuring that the LXT oscillator

is in the Quick Start operating mode. In the Quick Start Mode the LXT oscillator will power up and

stabilise quickly. However, after the LXT oscillator has fully powered up it can be placed into the

Low-power mode by setting the LXTLP bit high. The oscillator will continue to run but with

reduced current consumption, as the higher current consumption is only required during the LXT

oscillator start-up. In power sensitive applications, such as battery applications, where power

consumption must be kept to a minimum, it is therefore recommended that the application program

sets the LXTLP bit high about 2 seconds after power-on.

It should be noted that, no matter what condition the LXTLP bit is set to, the LXT oscillator will

always function normally, the only difference is that it will take more time to start up if in the Low-

power mode.

Internal 32kHz Oscillator – 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°C degrees, the fixed oscillation frequency of 32kHz will have a tolerance within 10%.

External Clock – EC

The system clock can also be supplied by an externally supplied clock giving users a method of

synchronizing their external hardware to the microcontroller operation. This is selected using a

configuration option and supplying the clock on pin OSC1. Pin OSC2 should be left floating if the

external oscillator is used. The internal oscillator circuit contains a filter circuit to reduce the

possibility of erratic operation due to noise on the oscillator pin, however as the filter circuit

consumes a certain amount of power, a oscillator configuration option exists to turn this filter off.

Not using the internal filter should be considered in power sensitive applications and where the

externally supplied clock is of a high integrity and supplied by a low impedance source.

Supplementary Oscillators

The low speed oscillators, in addition to providing a system clock source are also used to provide a

clock source to two other device functions. These are the Watchdog Timer, the LCD driver and the

Time Base Interrupts.

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