Almost all of the 8051 variants that I have looked at with multiple data pointers have a description of how they work in either the part data sheet or the vendors part family users manual. Now ...... while most dual data pointer implementations are aimed at speeding up block move type operations there are differences in how various vendors have implemented the scheme. So it is essential to become fully familiar with the variant you select before trying to write code that takes advantage of its dual data pointers.

Michael Karas