Your code compiles fine, addresses the correct piece of memory, and should do what you want.

Is your problem "How to use FLIP"
or "How to wire your RAM chip"

You should read your data sheet to see the significance of the bits of the AUXR register.

Some devices have "on-chip XRAM". Most regular 8051s just access external RAM with just the regular MOVX instruction. You do not set any registers at all. You only need contortions to use the "on-chip" XRAM.

David.