satya,

I understand that you want the Internal ROM and the External Rom to look contiguous to a single binary program file.

This is do-able but you might want to re-think the proposition. I know of no single file, single burn</> way to do this unless you have a home brew programmer that you can modify the code for.

Now here is exactly what you shouldn't do

If you write in assembler you can read your listing file after final link and look for the partition address (where internal crosses into external) and re-edit you source file to "ORG" the External PROM listing at the start of the External Rom's Addrs. If an instruction "breaks" accross the addressing boundry then pad it with NOPs.

You end up with two files a low address file for the internal ROM and an upper address file for the external ROM.

The above is a maintenance nightmare so don't make a mistake.

Here is a better idea

Partition the code to place "housekeeping" (serial rx/tx, number conversion, sorts) and "infra-structural" code (interrupt routines, initialization) in the Internal Rom and designate them as "PUBLIC". These routines most likely will not change much.

Place routines that call these low level routines (as Externals) into the larger external ROM (ORG'd at the ROM start address) .

Your code might require some tough re-consideration but you will end up with a "scheme" that is easily modified and maintained.

regards,
p