Want to start writing AS 3.0 or use Flex 2.0, but need to use them alongside older elements created in AS 2.0 and published for Flash Player 8 or lower? You could use LocalConnection or ExternalInterface, both having their own limitations, or you could take a look at FlashInterface.
FlashInterface allows direct communication between AVMs with a common API for both AS 2.0 and AS 3.0. It also supports controlling Flash Player 7 and lower SFW’s through a Flash 8 wrapper.
Features
Bi-direction communication between AVMs, Synchronous calls, Returns values from within same call, Common API, Call Local Properties, Call Local Methods, Anonymous Calls, Global Access to SWF elements, Optional Event Listener Model, No limitation on data size.