A built-in apparatus includes a response time buffer (11) that stores a response time, a calculation result buffer (14) that stores a calculated frame, and a transmission part (130). The transmission part (130) obtains second data and start processing for calculating a frame check sequence from the second data, upon receiving a transmission command (310), judges whether frame transmission processing for generating and transmitting the second data and the frame check sequence calculated from the second data as a response frame (320) will be completed within the response time, and transmits the calculated frame stored in the calculation result buffer (14) as the response frame (320) when judging that the frame transmission processing will not be completed within the response time.