Circuit basics(6):pull up & pull down

The purpose of pull up/down is to insure that a circuit has a default value (high, or low), given no other input:

a pull up resistor (connect to a power supply) pulls the line high;

a pull down resistor(connect to ground) pulls the line down.

    

Pull-up resistor                                    pull-down

http://www.seattlerobotics.org/encoder/mar97/basics.html

 Example
MON_INT_N[2] is connected to OM5_GPIO8_233. INT2 pad can be configured as active high; GPIO is configured as input (internal pull up/pull down disabled; high level detection).
open_drain_2 open_drain_1
 When MON drives 3.3V (high), the downside of R14130, closer to MON, is 2.5V due to 1.8V (R13993) pull-up.
Note: INT2 pad can be configured to open-drain, too. I assume that the “NB” resisters are there, in case the pad is configured as open drain?

 

 

 

 

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