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LV24- v6 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 RD8 pin with the relevant DIP switch SW8, jumper J8 and RD8 push
button with jumper J17 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 the PORTD port pins to be
connected to pull-down resistors, it is necessary
to place jumper J8 in the
Down
position first.
This enables any PORTD port pin to be supplied
with a logic zero (0V) in idle state over jumper J8
and 8x10k resistor network. To provide the RD8
pin with such signal, it is necessary to set switch
P1 on the DIP switch SW8 to ON position.
As a result, every time you press the RD8 push
button, a logic one (VCC-3.3 voltage) will appear
on the PG2 pin, provided that jumper J17 is
placed in the VCC-3.3 position.
In order to enable port PORTD 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 J8 in the
Up
position
and jumper J17 in the GND position. This
enables any port PORTD input pin to be driven
high (3.3V) in idle state over the 10k resistor.
As a result, every time you press the RD8 push
button, a logic zero (0V) will appear on the RD8
pin, provided that the P1 switch is set to the ON
position.
In case that jumpers J8 and J17 have the same
logic state, pressure on any button will not cause
input pins to change their logic state.
Figure 20-5
: Jumper J8 in pull-down and jumper J17 in pull-up position
Figure 20-6:
Jumper J8 in pull-up and jumper J17 in pull-down position
Figure 20-7:
Jumpers J8 and J17 in the same position
