A data transfer control device includes: a transmitter circuit; a receiver circuit; a transfer direction switch circuit which performs switching a transfer direction; a transfer direction switch indication circuit which indicates the transfer direction switch circuit to switch the transfer direction; and a code generation circuit which generates a transfer direction switch request code when a transfer direction switch request has been received from an upper layer circuit. When the transfer direction switch request has been received from the upper layer circuit, the transmitter circuit transmits the transfer direction switch request code through a serial signal line, and the transfer direction switch indication circuit indicates the transfer direction switch circuit to switch from a transmission direction to a reception direction after the transfer direction switch request code has been transmitted.