We have one design constraint to use two flash connected in parallel: First flash uses (D0-D15) and second flash uses D16 - D31. Using same physically address for both flash with available 28 bit address bus using A1 - A19. For example, When we write double word into flash, it is as good as writing first word into first flash and second word into second flash.
We need to know how to send commands to both flash at same time for operation like READ or WRITE. Both flash shares same CE, OE & WE.