HT46R005 datasheet(21/62 Pages) HOLTEK

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HT48R005/HT46R005

Rev. 1.00

November 29, 2011

Internal RC Oscillator

- HIRC

The internal RC oscillator is a fully integrated system os-

cillator 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 fre-

quency 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 degrees, the fixed oscilla-

tion frequency of 4MHz, 8MHz or 12MHz will have a tol-

erance within 2%. Note that if this internal system clock

option is selected, as it requires no external pins for its

operation, I/O pins PA5 and PA6 are free for use as nor-

mal I/O pins.

Internal Low Speed Oscillator

- LIRC

The LIRC is a fully self-contained free running on-chip

RC oscillator with a typical frequency of 13kHz at 5V re-

quiring no external components. When the device en-

ters the Sleep Mode, the system clock will stop running

but the WDT oscillator continues to free-run and to keep

the watchdog active. However, to preserve power in cer-

tain applications the LIRC can be disabled via a configu-

ration option.

Operating Modes

The system can be selected to operate in two modes.

These Modes are Normal and Sleep.

Operating

Mode

OSC1/OSC2 Configuration

HXT

ERC

HIRC

Normal

Run

Sleep

Stop

Operating Mode Control

Mode Switching

The devices are switched between one mode and an-

other using the HALT instruction. The HALT instruction

forces the system into the Sleep Mode.

When a HALT instruction is executed, the system enters

the Sleep mode the following conditions exist:

· The system oscillator will stop running and the appli-

cation program will stop at the

²HALT² instruction.

· The Data Memory contents and registers will maintain

their present condition.

· The WDT will be cleared and resume counting if the

WDT clock source is selected to come from the WDT

oscillator. The WDT will stop if its clock source origi-

nates from the system clock.

· The I/O ports will maintain their present condition.

· In the status register, the Power Down flag, PDF, will

be set and the Watchdog time-out flag, TO, will be

cleared.

Standby Current Considerations

As the main reason for entering the Sleep Mode is to

keep the current consumption of the MCU to as low a

value as possible, perhaps only in the order of several

micro-amps, there are other considerations which must

also be taken into account by the circuit designer if the

power consumption is to be minimised.

Special attention must be made to the I/O pins on the

device. All high-impedance input pins must be con-

nected to either a fixed high or low level as any floating

input pins could create internal oscillations and result in

P A 5 / P A 6 u s e d a s n o r m a l I / O s

N o t e :

I n t e r n a l R C

O s c i l l a t o r

P A 5 / O S C 2

P A 6 / O S C 1

Internal RC Oscillator

- HIRC

H X T

E R C

H I R C

M U X

C o n f i g u r a t i o n o p t i o n

L X T

M U X

( S L O W )

( N o r m a l )

L I R C

M U X

T o w a t c h d o g t i m e r

f H X T

f E R C

f H I R C

f L X T

f L I R C

f S Y S

f S Y S / 4

C L K M O D

( D e t e r m i n e N o r m a l /

S l o w M o d e )

C o n f i g u r a t i o n o p t i o n

System Clock Configurations

HT46R005 数据表(PDF) 21 Page - Holtek Semiconductor Inc

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HT46R005 数据表(PDF) 21 Page - Holtek Semiconductor Inc

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