The CALL or JMP instructions have no need to identify any differences. All these instructions do is provide the address of where to go next. This next address is shoved into the PC (program counter) and it is then the job if the intstuction fetch circuit of the part of the processor to look at the address and determine where to go to fetch the data. In the case of your part, provided you have all the controls setup properly, the fetch circuit simply looks at address and says if from 0 -> sizeof(internal FLASH)-1 then fetch from internal space. If it sees address from sizeof(internal FLASH) -> 0xFFFF then go to external memory bus and run a cycle there.

Michael Karas