Data writing processing into memory of a semiconductor memory device by using a memory of a host device

An information processing device comprising a host device and a semiconductor memory device,

• the host device comprising a main memory, and
• the semiconductor memory device comprising a nonvolatile semiconductor memory which stores first address conversion information and data,
• a memory unit which stores second address conversion information, the second address conversion information being part of the first address conversion information, and
• a controller which accesses the nonvolatile semiconductor memory by referring to the second address conversion information,
• wherein third address conversion information is stored in the main memory, the third address conversion information being part of or all of the first address conversion information, and the controller uses the third address conversion information when accessing the nonvolatile semiconductor memory if address conversion information to be referred is not stored in the second address conversion information.