Sleep mode and wake up

I want to sleep my arduino uno for 2 minute, then wake it up.
How can i achieve that.

Seen this?
http://playground.arduino.cc/Learning/ArduinoSleepCode

MarkT:
Seen this?
Arduino Playground - HomePage

Yeah i have seen that i have already done code based on that.
i already get it working for 20s(via timer interrupt) but i need for atleast two minute.

basically asking for logic i am working in idle mode.

I found many sleep libraries to be a minefield.
This one however works as desired with no surprises.

Sleep_n0m1

Dear George thanks a lot