When officially is the ball ready for play?

[jontheref]

I've been through this play where the team was set awaiting us with one second left. There is nothing by rule that stipulates the team must be set after the whistle....only that they all be set prior to the snap. In our play, they got off the play with one second, through a fade to the end zone--saw a flag for dpi....where they got another play...and a score for a tie game. No controversey there, eh? But, yes, the play was a legal play.