To recognize whether or not data are normally written to a memory device in the host device of a data transfer origin without obstructing the transfer of real data.

When the host device 1 requests the write of sector data, a host adapter 2 deblocks the sector data into block data and transfers them to a memory adapter 4 by a block data unit. The memory adapter 4 writes the block data to the memory device 5, also generates a block CRC code from the block data and returns it to the host adapter 2 as a write reply. At the time of receiving the block CRC code, the host adapter 2 performs CRC computation, restores the CRC code of the entire sector data, checks matching with the CRC code of original sector data and reports a checked result to the host device 1.