AT89C5122D-RDRUM datasheet(170/208 Pages) ATMEL

170 / 208 page

170

AT83R5122, AT8xC5122/23

4202F–SCR–07/2008

Microcontroller Reset

Introduction

The internal reset is used to start up (cold reset) or to re-start (warm reset) the micro-

controller activity. When the reset is applied (active state), all internal registers are

initialized so that the microcontroller starts from a known and clean state for the program

always runs as expected.

The reset is released (inactive state) when the following conditions are internally met :

–

The power supply has reatched a minimum level which garantees that the

microcontroller works properly

–

The on-chip oscillator has reached a minimum oscillation level which

ensures a good noise to signal ratio and a correct internal duty cycle

–

the active state duration is at least two machine cycles.

If one of the above conditions is not met the microcontroller is not correctly reset and

might not work properly.

The internal reset comes from four different sources :

–

Reset pin

–Power On Reset (POR)

–

Power Fail Detector (PFD)

–

Hardware Watch-Dog Timer (WDT)

Figure 100.

Reset bock diagram

Watch Dog

RST

Internal Reset

Timer

Microcontroller

Vcc

3.3V Internal

Digital Regulator

C51

Core

VCore

POR

PFD

AT89C5122D-RDRUM 数据表(PDF) 170 Page - ATMEL Corporation

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