23
UNI-DS3 Development System
MikroElektronika
page
Pull-up/pull-down resistors enable you to set the logic level on all microcontroller’s input pins when they are in idle state. Such level
depends on the position of the pull-up/pull-down jumper. The RB1 microcontroller pin with jumper J2 and the RB1 push button with
jumper J10 are used here for the purpose of explaining the performance of pull-up/pull-down resistors. The principle of their operation
is the same as for all other microcontroller pins.
In order to enable connection between the
PORTB port and pull-down resistors, it is
necessary to place jumper J2 in the
Down
SRVLWLRQ¿UVW,QWKLVZD\DQ\3257%SRUWSLQFDQ
be supplied with a logic zero (0V) in idle state
over jumper J2 and 8x100K resistor network.
As a result, every time you press the RB1 push
button, a logic one (VCC voltage) will appear on
the RB1 pin, provided that jumper J10 is placed
in the VCC position.
In order to enable port PORTB pins to be
connected to pull-up resistors and the port input
pins to be supplied with a logic zero (0), it is
necessary to place jumper J2 in the
Up
position
and jumper J10 in the GND position. This enables
any port PORTB input pin to be driven high (5V)
in idle state over the 100K resistor. As a result,
every time you press the RB1 push button, a
logic zero (0V) will appear on the RB1 pin.
In case that jumpers J2 and J10 have the same
logic state, pressure on any button will not cause
input pins to change their logic state.
)LJXUH
: Jumper J2 in pull-down and jumper J10 in pull-up position
)LJXUH
Jumper J2 in pull-up and jumper J10 in pull-down position
)LJXUH
Jumpers J2 and J10 in the same position
