HT66F13 datasheet(32/173 Pages) HOLTEK

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OperatingModesandSystemClocks

Present day applications require that their microcontrollers have high performance but often still

demand that they consume as little power as possible, conflicting requirements that are especially true

in battery powered portable applications. The fast clocks required for high performance will by their

nature increase current consumption and of course vice versa, lower speed clocks reduce current

consumption. As Holtek has provided these devices with both high and low speed clock sources and

the means to switch between them dynamically, the user can optimise the operation of their

microcontroller to achieve the best performance/power ratio.

SystemClocks

The device has many different clock sources for both the CPU and peripheral function operation. By

providing the user with a wide range of clock options using configuration options and register

programming, a clock system can be configured to obtain maximum application performance.

The main system clock can come from a high frequency fH or low frequency fL source and is selected

using the HLCLK bit and CKS2~CKS0 bits in the SMOD register. The high speed system clock can be

sourced from either a HXT, ERC or HIRC oscillator, selected via a configuration option. The low

speed system clock source can be sourced from internal clock fL. If fL is selected, then it can be sourced

by the LIRC oscillator. The other choice, which is a divided version of the high speed system oscillator

has a range of fH/2~fH/64. Note that when the system clock source fSYS is switched to fL from fH, the high

speed oscillation will stop to conserve the power. Thus there is no fH~fH/64 for peripheral circuit to use.

There are two additional internal clocks for the peripheral circuits, the substitute clock, fSUB, and the

Time Base clock, fTBC. These internal clocks are sourced by the LIRC oscillator. The fSUB clock is used

to provide a substitute clock for the microcontroller just after a wake-up has occurred to enable faster

wake-up times. Together with fSYS/4 it is also used as one of the clock sources for the Watchdog timer.

The fTBC clock is used as a source for the Time Base interrupt functions and for the TMs.

SystemOperationModes

There are six 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 are two modes allowing normal operation of the

microcontroller, the NORMAL Mode and SLOW Mode. The remaining four modes, the SLEEP0,

SLEEP1, IDLE0 and IDLE1 Mode are used when the microcontroller CPU is switched off to conserve

power.

OperationMode

Description

CPU

fSYS

fSUB

fTBC

NORMALMode

fH~ fH/64

SLOWMode

IDLE0Mode

Off

On/Off

IDLE1Mode

Off

SLEEP0Mode

Off

SLEEP1Mode

Off

HT66F13/HT66F14/HT66F15

EnhancedA/DFlashType MCU

Rev.1.10

February9,2011

HT66F13 датащи(PDF) 32 Page - Holtek Semiconductor Inc

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