AT83EB5114_08 datasheet(9/95 Pages) ATMEL

9 / 95 page

AT89/83EB5114

4311C–8051–02/08

Power Monitor

The Power Monitor function supervises the evolution of the voltages feeding the micro-

controller, and if needed, suspends its activity when the detected value is out of

specification.

It warrants proper startup when AT8xEB5114 is powered up and prevents code execu-

tion errors when the power supply becomes lower than the functional threshold.

This chapter describes the functions of the power monitor.

Description

In order to startup and to properly maintain the microcontroller operation, Vcc has to be

stabilized in the Vcc operating range and the oscillator has to be stabilized with a nomi-

nal amplitude compatible with logic threshold.

In order to be sure the oscillator is stabilized, there is an internal counter which main-

tains the reset during 1024 clock periods in case the oscillator selected is the OSC A

and 64 clock periods in case the oscillator used is OSC B or OSC C.

This control is carried out during three phases: the power-up, normal operation and

stop. In accordance with the following requirements:

•

it guarantees an operational Reset when the microcontroller is powered-up, and

•

a protection if the power supply goes below minimum operating Vcc

Figure 2. Power Monitor Block Diagram

Power Monitor diagram

The Power Monitor monitors the power-supply in order to detect any voltage drops

which are not in the target specification. The power monitor block verifies two kinds of

situation that may occur:

•

during the power-up condition, when Vcc reaches the product specification,

•

during a steady-state condition, when Vcc is at nominal value but disturbed by any

undesired voltage drops.

Figure 2 shows some configurations which can be handled by the Power Monitor.

External

Power-Supply Vcc

Internal RESET

Power Fail

Detector

Power up

Detector

AT83EB5114 Datasheet(PDF) 9 Page - ATMEL Corporation