Memory system in which extended function can easily be set

A host system to use a memory device, the memory device including a nonvolatile semiconductor memory device, the host system is accessible to a memory space and an extension register space of the nonvolatile semiconductor memory device, and the host system can control an extended function section through extension register set which is placed in the extension register space,

• wherein an information register in the extension register space indicates information which is configured to specify a type of the extended function and a controllable driver, and address information indicating a place where an register for controlling the extended function is stored,
• the control section is arranged to process a first command to read data from the extension register space in accordance with designations of the address information and data length, and a second command to write data to the extension register space in accordance with designations of the address information and data length,
• the host system comprising a host driver and a system memory,
• wherein the host driver uses the first command to read a function identification code, a manufacturer identification information, and a function identification information from the information which is described in the information register in the extension register space, and specify a usable general-purpose function driver or a dedicated function driver and, when a driver exists, the host driver loads the driver into the system memory, and execution of the function driver initializes the extended function in the memory device.