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Development System EasydsPIC6
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. This level
depends on the position of the pull-up/pull-down jumpers. The RD0 pin with the relevant DIP switch SW3, jumper J3 and push button
RD0 with jumper J15 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 J3 in the
Down
position first.
This enables any PORTD port pin to be supplied
with a logic zero (0V) in idle state over jumper J3
and 8x10k resistor network. To provide the RD0
pin with such signal, it is necessary to set switch
1 on the DIP switch SW3 to ON position.
As a result, every time you press the RD0 button,
a logic one (VCC) will appear on the RD0 pin,
provided that jumper J15 is placed in the VCC
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 J3 in the
Up
position
and jumper J15 in the GND position. This
enables any port PORTD input pin to be driven
high (5V) in idle state over the 10k resistor.
As a result, every time you press the RD0 push
button, a logic zero (0V) will appear on the RD0
pin, provided that switch 1 on the DIP switch
SW3 is set to ON position.
In case that jumpers J3 and J15 have the same
logic state, pressure on any button will not cause
input pins to change their logic state.
Figure 22-5
: Jumper J3 in pull-down and jumper J15 in pull-up position
Figure 22-6:
Jumper J3 in pull-up and jumper J15 in pull-down position
Figure 22-7:
Jumpers J3 and J15 in the same position
