Haven't found much luck with discrete codes for this unit, including a VERY disappointing call to Panasonic for support. NOT. However, I did get a couple of useful answers (one from Kevin Patz) which recommended building up series of commands to create the function of the discretes. For example, source input can be simulated by channel up/channel down/toggle source N times. N=2 gets you to Component 1.

Love the TV, just wish the remote was more standard, or at least documented.