There are two things
worth attention concerning the microcontroller power supply circuit:
Brown-out
It is a potentially
dangerous state which occurs at the moment the microcontroller is being turned off or in
situations when power supply voltage drops to the limit due to electric noise. As the
microcontroller consists
of several circuits which have different operating voltage levels, this state can
cause its out-of-control
performance. In order to prevent
it, the microcontroller usually has built-in circuit for brown out reset. This circuit immediately resets the
whole electronics when
the voltage level drops below the limit.
Reset pin
It is usually marked as
MCLR (Master Clear
Reset) and serves for external reset of the
microcontroller by applying logic zero (0) or one (1), depending on type of the
microcontroller. In case the brown
out circuit is not built in,
a simple external circuit for brown out reset can be connected to this pin.
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