Hello, we need to know the part number. It may indeed be that the LCD is split into two parts, each with a separate controller, it is more likely, however, that there are two chip select pins, and that each needs to be set to a specific logic level to acces the LCD controller. Sometimes one needs to be high and the other needs to be low, this gives the circuit designer a degree of choice, he(she) can use the chip select polarity that suits the chosen host controller, and tie the remaining chip select to the appropriate level. If you have a pin-out list for the device, it may be that one of the pins is shown as /cs1 or /cs2. You will probably already know that this indicates an active low pin.