BOOT greater than 512KB

Dear all.

We have a DM642 based card, and we build an aplication and then we convert
coff file to ascii hex to program flash.
But the hex file it's greater than 512 KB.
We need to select on boot.asm external address to cover range greater than
512KB of the flash. We have a CPLD that has a register ,located at
0xA000081,that manages external address like A19 to A24.
What modifications i have to do on boot.asm to boot can load all data from
flash to SDRAM.
I did this:
    stw	      a3,*+b15[0x6]
    nop	      2
    mvk       0x0081,a3
||  or	      0,a3,b5
    mvkh      0xa0000000,a3
||  extu      b5,10,29,b5
    stb       b5,*+a3[0x0]
    nop       2		
    ldw	      *+b15[0x6],a3
    nop	      4

when i copy something from flash to SDRAM but it doesn't work.		
Anyone has idea how can i do that?

Best regards,

Rui Silva