Peter,

That's the whole point of PDATA: it provides quicker access to one page (256 bytes) of XDATA.
The page is defined by P2.
The possibility to use R1 & R2 also effectively gives you a "Dual Data Pointer" within PDATA.

These are part of what I meant by "the general principles of PDATA"

But what are the specific issues with the Triscend E5 devices?