external pull-up resistor for microcontroller

Does all four-ports of 89S52 require pull up resistors?
some circuit use pull-ups on all ports...As per data sheet it is needed to use pull-up for port P1 only and others having internal pull-ups..

hi karthikdm

Does all four-ports of 89S52 require pull up resistors?

89s52 has 4 ports p0, p1, p2 and p3
all ports has internal pull ups except port 0
port0 needed external pull ups

some circuit use pull-ups on all ports

controller pin's output current is too low some time we need more current then we use external one to by force providing a current even internal pull up exist

As per data sheet it is needed to use pull-up for port P1 only and others having internal pull-ups..

i think u mis understand the pdf
only port 0 need pull ups of 10 k recommended but can be used less

Hi khartik, Majoka is right. Only P0 needs pull ups but sometimes base on my experience even other ports needs pull ups or pull down depends on your design.

Thanks clear now...yes majoka its P0 ..not P1

hi karthikdm
you r always welcome dear