HT45R35 datasheet(14/59 Pages) HOLTEK

14 / 59 page

HT45R35

Rev. 1.30

May 14, 2010

Reset

There are three ways in which a reset can occur:

· RES reset during normal operation

· RES reset during HALT

· WDT time-out reset during normal operation

A WDT time-out, when the device is in the Power Down

mode, is different from other device reset conditions, in

that it can perform a

²warm reset² that resets only the

Program Counter and the Stack Poiner, leaving the

other circuits in their original state. Some registers re-

main unchanged during other reset conditions. Most

registers are reset to their

²initial condition² when the re-

set conditions are met. By examining the PDF and TO

flags, the program can distinguish between the different

device reset types.

PDF

RESET Conditions

RES reset during power-up

RES reset during normal operation

RES wake-up HALT

WDT time-out during normal operation

WDT wake-up HALT

Note:

²u² means ²unchanged²

To guarantee that the system oscillator is started and

stabilised, the SST or System Start-up Timer, provides

an extra-delay of 1024 system clock pulses when the

system is reset (power-up, WDT time-out or RES reset)

or when the system awakens from a Power Down state.

When a system reset occurs, the SST delay is added

during the reset period. Any wake-up the Power Down

mode will enable the SST delay.

An extra option load time delay is added during a system

reset (power-up, WDT time-out during normal mode or a

RES reset).

The functional unit device reset status are shown below.

Program Counter

000H

Interrupt

Disable

Prescaler

Clear

WDT

Clear. After master reset,

WDT begins counting

Timer/Event Counter

Off

Input/Output Ports

Input mode

Stack Pointer

Points to the top of the stack

W a r m R e s e t

W D T

H A L T

C o l d

R e s e t

R E S

S y s t e m R e s e t

S S T

1 0 - b i t R i p p l e

C o u n t e r

O S C 1

Reset Configuration

R E S

V D D

1 0 0 k W

1 0 k W

0 . 0 1 m F

R E S

V D D

1 0 0 k W

0 . 1 m F

B a s i c

R e s e t

C i r c u i t

H i - n o i s e

R e s e t

C i r c u i t

Reset Circuit

Note:

Most applications can use the Basic Reset Cir-

cuit as shown, however for applications with ex-

tensive noise, it is recommended to use the

Hi-noise Reset Circuit.

t S S T

R E S

V D D

S S T T i m e - o u t

C h i p R e s e t

Reset Timing Chart

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