Define the ports of AT89C51 as input or output.

I m using AT89C51 for digital clock, with external clock.

i want to set the port0-1-2 for parallel data, and port3 for serial data

the problem is to define the port as input or Output

Master Clock
------------------
port0 for input
port1 for output
port2 for output
port3 for output (to send serial data)

Slave Clock
------------------
port0 for output
port1 for output
port2 for output
port3 for input (to receive data)

please tell me how can i set the ports for input and/or as outpur