Image pickup apparatus and interchangeable lens

An interchangeable lens attachable to an image pickup apparatus, the lens comprising:

• first and second terminals for communication with the image pickup apparatus;
• and
• a lens side control unit configured to transmit, when communication is made with the image pickup apparatus with the lens attached, in a first communication mode in which a clock signal is input via the first terminal and communication is performed based on the clock signal, data that indicates the interchangeable lens is available for a second communication mode in which communication is performed without inputting the clock signal via the first terminal,
• wherein the lens side control unit receives a predetermined signal for baud rate adjustment of the second communication mode via the second terminal, and communicates with the image pickup apparatus in the second communication mode at a baud rate determined by the image pickup apparatus.

A method of controlling an image pickup apparatus to which an interchangeable lens is attachable, that includes first and second terminals for communication with the interchangeable lens, the method comprising:

• judging, when the communication is made with the attached interchangeable lens, in a first communication mode in which a clock signal is output via the first terminal and communication is performed based on the clock signal, whether or not the attached interchangeable lens is available for a second communication mode in which communication is performed without outputting the clock signal via the first terminal,
• continuing the first communication mode when it is judged that the interchangeable lens is unavailable for the second communication mode,
• transmitting a predetermined signal for baud rate adjustment of the second communication mode via the second terminal, and
• determining a baud rate of the second communication mode when it is judged that the interchangeable lens is available for the second communication mode.