HT95R25 datasheet(28/51 Pages) HOLTEK

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HT95R25

Rev. 1.00

March 6, 2009

Reset (Power-on)

RES Reset

(Normal/Green)

RES Reset

(Sleep/Idle)

WDT Time-out

(Normal/Green)

WDT Time-out

(Sleep/Idle)

MODE

000

- ----

00u

- ----

00u

- ----

00u

- ----

00u

- ----

MFIC

- 000 - 000

- uuu - uuu

PFDC

0000

----

0000

----

0000

----

0000

----

uuuu

----

PFDD

0000 0000

uuuu uuuu

Note:

²u² stands for unchanged

²x² stands for unknown

²-² stands for unimplemented

HALT

Instruction

MODE1

MODE0

UPEN

Operation

Mode

32768Hz

3.58MHz

System

Clock

Not executed

Normal

3.58MHz

Not executed

Green

OFF

32768Hz

Executed

Sleep

OFF

Stopped

Executed

Idle

OFF

Stopped

Note:

²X² means don¢t care

MODE0 will be cleared to 0 automatically after wake-up from Idle Mode.

Oscillator

There are two oscillator circuits within the controller.

One is for the system clock which uses an externally

connected 32768Hz crystal. The other is an internal

watchdog oscillator.

System Crystal/Ceramic Oscillator

The system clock is generated using an external

32768Hz crystal or ceramic resonator connected be-

tween pins X1 and X2. From this clock source an inter-

nal circuit generates a 3.58MHz clock source which is

also required by the system. This frequency generator

circuit requires the addition of externally connected RC

components to pin XC to form a low pass filter for the

3.58MHz output frequency stabilisation.

Watchdog Timer Oscillator

The WDT oscillator is a fully integrated free running RC

oscillator with a typical period of 65

ms at 5V, requiring no

external components. It is selected via configuration op-

tion. If selected, when the device enters the Power

Down Mode, the system clock will stop running, how-

ever the WDT oscillator will continue to run and keep the

watchdog function active. However, as the WDT will

consume a certain amount of power when in the Power

Down Mode, for low power applications, it may be desir-

able to disable the WDT oscillator by configuration op-

tion.

Operation Mode, Power-down and

Wake-up

There are four operational modes, known as the idle

mode, sleep mode, green mode, and normal mode. The

chosen mode is selected using the MODE0, MODE1

and UPEN bits in the PFDC register but also depends

upon whether the HALT instruction has been executed

or not.

Idle Mode

When the device enters this mode, the normal operating

current, will be reduced to an extremely low standby cur-

rent level. This occurs because when the device enters

the Power Down Mode, both the 3.58MHz and 32768Hz

system oscillators are stopped which reduces the power

consumption to extremely low levels, however, as the

device maintains its present internal condition, it can be

woken up at a later stage and continue running, without

requiring a full reset. This feature is extremely important

in application areas where the microcontroller must

have its power supply constantly maintained to keep the

device in a known condition but where the power supply

capacity is limited such as in battery applications.

X 1

X 2

X C

1 5 k W

3 n F

4 7 n F

Crystal/Ceramic Oscillator

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