Use port or xdata method to bank is wast many roms..each bank must have the common area...how can i design a sch use gal to bank only one common area to save roms???
Take a look at the 32K common bank + N x 32K switched bank schemes. This scheme can use ports or xdata latches to control the banking hardware as well as the N x 64K bank scheme. The difference is in the address decoding hardware, not the source of the extra address bits. The 32K + 32K scheme will use 15 normal address bits, plus the bank bits when bit 15 = 1, while the N x 64 scheme will use 16 normal address bits, plus the bank bits.