Datasheet

7764A–8051–11/07

c) Using an external Brown-out device

Read application note “External Brown-out Protection for C51 microcontrollers with Active High

Reset Input“ (doc 4183).

Sometimes the RST pin may be internally forced by the POR or the PFD or the WDTso that the

external peripherals if any are reset at the same time as the MCU. While the POR or the PFD or

the WDT are active the RST pin operates as an output. Therefore the RST pin cannot be exter-

nally forced to a permanent level. If the external Brown-out device operates in this way, an

intermediate resistor Rint or a diode must be implemented between the Brown-out device and

the RST pin.

Brown-out device with an intermediate resistor

Brown-out device with a diode

RST

Internal Reset

Microcontroller

Brown-out

device

To other on-board

circuitry

Rint

Power Fail

Detector

Watchdog

Timer

Power On

Reset

VCC

RST