how to assign pin in shard bus?

i see the document of stratix_dev_borad, the sram .flash and Ethernet shared the address and date bus, but i donnot know why the shared address sram begin from FSE_A2,Ethernet from FSE_A1 and flash from FSE_A0?

if i make my ouw board also use shared bus ,what the principle when i assign the pin on the PCB, thank you !