Memory map?

Hello,

After booting kernel, I want to access the physical address in rom ,
for example:
my rom begins at 0xFE00 0000, and I want to read 1 byte at this address.

currently, the MMU has been turned on, the RAM begin at 0x0C00 0000,
and I don't know what the address of the ROM is.

what do I have to do?
is there anybody know how to take the address of the ROM?

Help me, pls.
Thank you,
Jari

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