pull up register doute

[ritesh]

i use p89v51rd2 if it is require to use pull up register at port.

 

i make led scrolling msg display.

 

if i use latch 74ls573 then it also require to use pull up register?

 

why pull up register is use.

[Amrith]

Ritesh,

Pull up resistiors are necessary at the port because the port pins of the controller are open drain or open collector.

Pull up register are used toenable internal pull up resistors.which deliver a very less current of about 2mA to 8mA. It is recommended to use external pull ups based on the load at pins.

[AJISH ALFRED]

 

Hi Ritesh,

This forum already have lot of posts related with the topic of pull up resistors

Please find the following links

http://www.engineersgarage.com/forums/8051/pull-resistor

http://www.engineersgarage.com/forums/electronics/pull-up-and-pull-down-resistors

[Author]

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