PURPOSE: To utilize both display functions by switching the display system to a packed pixel and a planar pixel by an external instruction without varying the constitution of a memory for storing color display data and a pallet register group.

CONSTITUTION: A selection address 19 for a packed pixel and a selection address 23 for a planar pixel are inputted to a selector circuit 24 and a physical address 5 of register selection is generated. Subsequently, by the circuit 24, registers of pallet register groups 13, 14 and 15 are selected. It is executed by converting the connection to the physical address 5 which can select the addresses 19, 23 from selection address generating circuits 16, 20 and the register groups 13 - 15. Also, in the address 5, the bit which is not connected to the selection address is fixed to logic of '1' or '0' by the circuit 24. In such a way, by switching the use pallet registers by the external instruction, both display functions of the planar pixel and the packed pixel can be utilized.