Memory control unit and memory system

A memory control unit includes fuses that are selectively blown to set a manufacturer's identification code (ID), and a further fuse that is selectively blown to designate the memory control unit as a general-purpose unit or a custom unit. When designated as a custom unit, the memory control unit uses the manufacturer's ID to protect data in the memory by scrambling the data, or by comparing the manufacturer's ID with an input ID and disabling access to the memory if the ID's do not match. A semiconductor integrated circuit chip including the memory control unit can thus be fuse-programmed for either general-purpose use or custom use.