Hi All, When I using debug mode in Keil C,I has a problem: MOV DPH,#0x80 MOV R0,#0x10 MOV A,#0x88 MOVX @R0,A THIS PROGRAM MEANS MOVE DATA 0x88 TO EXTERNAL MEMORY ADDRESS 0x8010, BUT WHY I CAN'T SEE THE CURRENT VALUE IN MEMORY WINDOW,It's my problem or it's a debug mode limit ? Thanks for your help.