Specifications

mikroElektronika | Free Online Book | PIC Microcontrollers | Chapter 8: Other MCU's Circuits
This is a special kind of Brown-out reset which occurs in
industrial environment when the power supply voltage “blinks”
for a moment and drops its value beneath minimal level. Even
short, such noise in power line may catastrophically affect the
operation of device.
Fig. 8-22 Noises
MCLR pin
Logic zero (0) on the MCLR pin causes immediate and regular reset. It is recommended to be connected as shown in figure
below. The function of additional components is to sustain “pure” logic one (1) during normal operation. If their values
are such to provide high logic level on the pin only upon T reset is over, the microcontroller will immediately start
operating. This feature may be very useful when it is necessary to synchronize the operation of the microcontroller with
additional electronics or the operation of several microcontrollers.
In order to avoid any error which may occur on Brown-out reset,
the PIC 16F887 has built in ‘defense mechanism’. It is a simple
but effective circuit which reacts every time the voltage power
supply drops below 4V and holds that level for more than 100
micro seconds. In that case, this circuit generates reset signal
and since that moment the whole microcontroller operates as if
it has just been switched on.
Fig. 8-23 Master Clear Pin
Previous Chapter | Table of Contents | Next Chapter
http://www.mikroe.com/en/books/picmcubook/ch8/ (15 of 15)5/3/2009 11:34:45 AM