Patent ID: 8494010

Claim:
A data transfer device comprising: a transmitting circuit that transmits data by using a packet to another data transfer device in a double data rate mode in which data is transferred at every rising and falling of a clock signal or in a single data rate mode in which data is transferred at every rising or at every falling of a clock signal, wherein the transmitting circuit includes a determining unit that determines whether to transmit data in the double data rate mode or in the single data rate mode; a setting unit that sets transfer mode information, which indicates the determined first or single data rate mode, in a predetermined bit in a header of the packet; an output unit that outputs data using the determined first or single data rate mode to the another data transfer device in synchronization with the clock signal; and a transmission control unit that, when a transfer mode determined by the determining unit has changed, instructs the setting unit to set transfer mode information indicating a transfer mode as changed in the packet and instructs the output unit to output data using the transfer mode as changed after outputting of a first packet in which a value indicating the transfer mode as changed is set is completed, and a receiving circuit that receives data transmitted from the another data transfer device in the double data rate mode or in the single data rate mode, wherein the receiving circuit includes a receiving unit that receives data transmitted from the another data transfer device in a predetermined one of the double data rate mode and the single data rate mode in synchronization with the clock signal; and a reception control unit that, when transfer mode information contained in the received data is different from the predetermined one of the first data transfer mode and the second data transfer mode, instructs the receiving unit to receive data using the transfer mode indicated by the transfer mode information after receiving the packet containing the transfer mode information as changed.