HT85F2270 datasheet(66/226 Pages) HOLTEK

66 / 226 page

Rev. 1.00

66 of ��6

�a� 1�� 01�

Standard 8051 8-Bit Flash MCU

HT85F2260/HT85F2270/HT85F2280

Operation Modes

There are three different modes of operation for the microcontroller, each one with its own

special characteristics and which can be chosen according to the specific performance and

power requirements of the application. There is one mode allowing normal operation of the

microcontroller, the NORMAL Mode, in which all oscillators and function remain active. There

are also two low power modes, the IDLE mode and the Power-Down Mode. In the IDLE mode,

the microcontroller CPU will stop and instruction execution will cease, however, the high speed

oscillators will continue to run and can continue to provide a clock source for the peripheral

functions such as WDT, Time Base, Timers, UARTs, I2C, SPI, ADC and DAC. The slow speed

oscillators will also continue to run and keep the WDT and Time Base functions active, if their

clock sources are not the system clock. In the Power-Down mode all oscillators are stopped and

therefore all functions cease operation.

Operating Mode

NORMAL Mode

IDLE Mode

Power-Down Mode

CPU Clock

Off

Peripheral Clock(Note)

Off

Low Frequenc� XTAL Oscillator (LXT)

On (LSOSEL=1)/Off On (LSOSEL=1)/Off

Off

Low Frequenc� Internal RC Oscillator (LIRC) On (LSOSEL=0)/Off On (LSOSEL=0)/Off

Off

High Frequenc� XTAL Oscillator (HXT)

On (HXTEN=1)/Off

Off

High Frequenc� Internal RC Oscillator (HIRC) On (HIRCEN=1)/Off On (HIRCEN=1)/Off

Off

Note: Peripheral Clock is the clock for Timer 0� Timer 1� Timer �� Timer �� PCA� UART0� UART1� I�C�

SPI� ADC� and DAC.

NORMAL Mode

As the name suggests this is the main operating mode where all of the selected oscillators and

clocks are active and the microcontroller has all of its functions operational and where the system

clock is provided directly by one of the high speed oscillators, HXT, HIRC or the PLL.

IDLE Mode

The IDLE Mode is entered when the IDL bit in the PCON register is set high. When the instruction

that sets the IDL bit high is executed the CPU operation will be inhibited, however, the high

frequency clock source will continue to run and can continue to provide a clock source for the

peripheral functions if selected. The low frequency clock sources will also remain operational and

can also provide a clock source for the WDT and Time Base functions, if they are enabled and if

their clock source is not selected to come from the system clock.

Power-Down Mode

The Power-Down Mode is entered when the PD bit in the PCON register is set high. When the

instruction that sets the PD bit high is executed the all oscillators will stop thus inhibiting both

CPU and peripheral functions such as the WDT and Time Base if they are enabled.

HT85F2270 Datasheet(PDF) 66 Page - Holtek Semiconductor Inc

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