FAS 123 ( R)

Guys, I am at work and need some help. If someone can quickly recap the tax implications of 123® etc it would be helpful. How do we get the tax benefit and the excess tax benefit in the OCF and FCF. Is there a deferred tax asset created when options are issued. Why and when does it get reversed ? Henceforth, I am keeping a copy of my cfa books handy.