HT48R52 datasheet(13/35 Pages) HOLTEK

13 / 35 page

HT48R52/HT48R53

Rev. 1.20

December 6, 2005

resets only the program counter and SP, leaving the

other circuits in their original state. Some registers re-

main unchanged during other reset conditions. Most

registers are reset to the

²initial condition² when the re-

set conditions are met. By examining the PDF and TO

flags, the program can distinguish between different

²chip resets².

TO 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 stands for ²unchanged²

To guarantee that the system oscillator is started and

stabilized, the SST (System Start-up Timer) provides an

extra delay of 1024 system clock pulses when the sys-

tem reset (power-up, WDT time-out or RES reset) or the

system awakes from the HALT state.

When a system reset occurs, the SST delay is added

during the reset period. Any wake-up from HALT will en-

able the SST delay.

An extra option load time delay is added during a system

reset (power-up, WDT time-out at normal mode or RES

reset).

The functional unit chip 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

R E S

V D D

1 0 0 k W

1 0 k W

0 . 1 m F *

0 . 0 1 m F *

Reset Circuit

Note:

²*² Make the length of the wiring, which is con-

nected to the RES pin as short as possible, to

avoid noise interference.

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

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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