Probably you meant MC9S12XEQ512?
It depends on what are you going to do with this RAM. In case all your data arrays are <=4kB (which is size of RAM R-page window), just surrend your banked RAM variable declarations and definitions with two pragmas.
#pragma DATA_SEG __RPAGE_SEG PAGED_RAM
//add your data here
#pragma DATA_SEG DEFAULT
Depending on your code you may need to change setting of Compiler for HC12 -> Code Generation -> Assume objects are in same page for = never for different objects.
