An electronic apparatus comprising: an interface section that is connected to a command/response line for receiving a command from a host device and transmitting a response to the host device and a data line for transmitting and receiving data, the data being transmitted or received while the data is divided into data blocks with a block size specified by the host device when the data length is a predetermined length or more; a data buffer that stores data; and a storage section wherein the interface section operates according to a rule of receiving the command, transmitting the response and receiving or transmitting the data in this order between the electronic apparatus and the host device, characterized in that when the interface section receives, via the command/response line, a a block size setting command for informing the electronic apparatus of transmitting information specifying the block size from the host device, the interface section transmits a response to the block size setting command to the host device via the command/response line, with the block size setting command not including information specifying the block size, and after transmitting the response to the block size setting command, the interface section receives, via the data line, the information specifying the block size from the host device and stores the information specifying the block size in the storage section, and when the specified block size is larger than a capacity of the data buffer, the interface section includes error information about incapability of accepting the block size in a response acknowledging receipt of an other command which is received after receiving the information specifying the block size, and transmits the response including the error information to the host device, wherein the other command is a command for informing the electronic apparatus of actually transmitting or receiving the data blocks with the block size created by dividing the data with the predetermined length or more from the host device, and the electronic apparatus does not accept the data blocks when receiving the divided data blocks according to said block size from the host device. an interface section that is connected to a command/response line for receiving a command from a host device and transmitting a response to the host device and a data line for transmitting and receiving data, the data being transmitted or received while the data is divided into data blocks with a block size specified by the host device when the data length is a predetermined length or more; a data buffer that stores data; and a storage section wherein the interface section operates according to a rule of receiving the command, transmitting the response and receiving or transmitting the data in this order between the electronic apparatus and the host device, characterized in that when the interface section receives, via the command/response line, a a block size setting command for informing the electronic apparatus of transmitting information specifying the block size from the host device, the interface section transmits a response to the block size setting command to the host device via the command/response line, with the block size setting command not including information specifying the block size, and after transmitting the response to the block size setting command, the interface section receives, via the data line, the information specifying the block size from the host device and stores the information specifying the block size in the storage section, and when the specified block size is larger than a capacity of the data buffer, the interface section includes error information about incapability of accepting the block size in a response acknowledging receipt of an other command which is received after receiving the information specifying the block size, and transmits the response including the error information to the host device, wherein the other command is a command for informing the electronic apparatus of actually transmitting or receiving the data blocks with the block size created by dividing the data with the predetermined length or more from the host device, and the electronic apparatus does not accept the data blocks when receiving the divided data blocks according to said block size from the host device.