When is the Supreme Court Deadlocked?

Today's per curiam affirming by an equally divided Court raises a question. The Court heard the case in question last month. At the end of that week, they must have voted in conference. The per curiam came out a month later. One inference that can be drawn is that there is some internal norm at the Court that--in the event of a tie--the Justices get a month to persuade each other or change their minds before a "hung Court" is declared. This is not the only possibility, but as far as I can tell an "equally divided Court" opinion almost never comes out the day of a conference or on the Monday following.