Pull down resistors

See Pull-up resistors

There is a safety problem when using a pull-down resistor.
When a contact is incorrectly configured as an output and set to 0(low level) and accidentally connected to the power, the pin can grill.

Part 2.
Here you can see a simple OR circuit with two types of pull-up(down) resistors.
The PD0 input has a pull-up resistor, and the PD1 input is connected to a pull-down resistor.
When buttons are unpressed.

You must use an inverting contact element in LDmicro when a pull-up resistor is used to bring the signal to a normal(positive) logic.

When buttons are pressed.