Hi,

May be this could be the reason...

In the second type of MOVX instrustion,the Data Pointer generates a 16-bit address.P2 outputs the high-order eight address bits(contents of DPH), while P0 multiplexes the low-order eight bits(DPL) with data.The P2 SFR retain its previous contents, while the P2 output buffers emit the contents of DPH.This form of MOVX is fater and more efficient when accessing very large data arrays, since no additional instructions are needded to set up the output ports

Rgds
Raj Shetgar