Hi M,By "package" I mean that you can get the PIC18F4620 in a 28 pin dip (soic), a 40 pin dip (soic) or a 44 pin TQFN.
That means that some pins are not there in the different packages (i.e. a 28 pin dip won't have as many pins as a 44 pin TQFN).
So, functionality gets moved around, depending on the package.
From what I'm seeing, the PIC18LF4431 is a 3.3v device and the PIC18F4620 is a 5v device.
Could there be some kind of level shifting needed?
Ah yes! They are both 44PIN TQFN and both are running at 3.3V.