1. An encoder configured to receive, from a control device, a request signal for requesting position data and transmit a response signal including the position data to the control device by serial communication, at a predetermined communication cycle, comprising:a response signal generating unit configured to generate a response signal including the position data and associated data associated with the position data; and
a transmitting unit configured to transmit the generated response signal,
wherein the transmitting unit is configured to transmit, of the position data and the associated data transmitted within one and the same communication cycle, the associated data prior to the position data when transmitting the response signal,
wherein the response signal generating unit continues to generate the position data while transmitting the associated data to the control device,
wherein the associated data includes at least one of data that the encoder acquires other than the position data, and data that is obtained in a process of generating the position data.