sleep mode for AT89C51CC01

hello all,
I am working with AT89C51CC01.
I want to make one program in which i have one i/p pin say P1_0.
If the pin state is not changed(from 1 to 0 or viceversa) in 1 minute 
then the program goes into Sleep mode.
and when the pin state is changed(from 0 to 1 or viceversa) then program 
comes out from sleep mode n continue to running normally.

please give ur idea oe sugestion for this problem.