AVR-Chat

Does anyone have information on the debugWIRE interface.  The 2 pages in
the Tiny13 datasheet are only enough to tell me that it exists, but are
inadequate to actually design an interface or write code.

I've searched Atmel's appnotes and all of the datasheets of their other
devices with debugWIRE (I think only the Tiny2313 and Tiny13 have it)
and have found no additional information.