Imaging apparatus and lens unit

1. An imaging apparatus to which a lens unit can be detachably mounted, comprising:

a first terminal and a second terminal for communication with the mounted lens unit; and

a control unit configured to perform switching between a first communication mode in which a clock signal is output via the first terminal and communication is performed with the lens unit via the second terminal based on the clock signal and a second communication mode in which communication is performed with the lens unit without outputting the clock signal,

wherein the control unit continues the first communication mode if it is determined that the lens unit is not available for the second communication mode,

wherein the control unit communicates with the lens unit in the second communication mode at a baud rate determined by the lens unit if it is determined that the lens unit is available for the second communication mode, and

wherein the control unit sets the second communication mode after a first signal notifying completion of baud rate settings is received from the lens unit.

2. The imaging apparatus according to claim 1 , wherein the control unit controls a signal level of the first terminal or the second terminal to keep at a predetermined level for a time corresponding to a predetermined clock count if it is determined that the lens unit is available for the second communication mode.

3. The imaging apparatus according to claim 2 , wherein the control unit transmits a second signal for instructing time measurement while the signal level of the first terminal or the second terminal is kept at the predetermined level, to the lens unit via the second terminal.

4. The imaging apparatus according to claim 1 , wherein the baud rate in the second communication mode is determined by the lens unit based on time measured by the lens unit in response to the second signal.

5. The imaging apparatus according to claim 1 , wherein the control unit measures time while a signal level of the first terminal or the second terminal is kept at a predetermined level by the lens unit if it is determined that the lens unit is available for the second communication mode, and transmits data on the measured time to the lens unit via the second terminal.

6. The imaging apparatus according to claim 5 , wherein the baud rate in the second communication mode is determined by the lens unit based on the data on the measured time transmitted from the control unit via the second terminal.

7. The imaging apparatus according to claim 1 , further comprising:

a temperature detection unit configured to obtain information indicating internal temperature of the imaging apparatus,

wherein the control unit transmits information instructing to set the baud rate again based on a detection result obtained by the temperature detection unit, in the second communication mode, to the lens unit.

8. The imaging apparatus according to claim 1 , wherein the control unit transmits a second signal for baud rate adjustment of the second communication mode to the lens unit via the second terminal if it is determined that the lens unit is available for the second communication mode.

9. A lens unit attachable to an imaging apparatus, comprising:

a first lens terminal and a second lens terminal for communication with the imaging apparatus; and

a lens control unit configured to perform switching between a first communication mode in which a clock signal is input via the first lens terminal and communication is performed with the imaging apparatus via the second lens terminal based on the clock signal and a second communication mode in which communication is performed with the imaging apparatus without inputting the clock signal,

wherein the lens control unit determines a baud rate to be used in the second communication mode and transmits a first signal notifying completion of baud rate settings to the imaging apparatus.

10. The lens unit according to claim 9 , wherein the lens control unit measures time while a signal level of the first lens terminal or the second lens terminal is kept at a predetermined level by the imaging apparatus, and determines the baud rate to be used in the second communication mode based on the measured time.

11. The lens unit according to claim 9 , wherein the lens control unit controls a signal level of the first lens terminal or the second lens terminal to keep at a predetermined level for a time corresponding to a predetermined clock count.

12. The lens unit according to claim 11 , wherein the lens control unit receives data on time while the signal level of the first lens terminal or the second lens terminal to keep at the predetermined level measured by the imaging apparatus via the second lens terminal, and determines the baud rate to be used in the second communication mode based on the received data.

13. The lens unit according to claim 9 , wherein the lens control unit receives a second signal for baud rate adjustment of the second communication mode from the imaging apparatus via the second lens terminal.

14. A method of controlling an imaging apparatus to which a lens unit can be detachably mounted, that includes a first terminal and a second terminal for communication with the mounted lens unit, the method comprising:

switching between a first communication mode in which a clock signal is output via the first terminal and communication is performed with the lens unit via the second terminal based on the clock signal and a second communication mode in which communication is performed with the lens unit without outputting the clock signal, and

determining whether the lens unit is available for the second communication mode or not,

wherein the first communication mode is continued if it is determined that the lens unit is not available for the second communication mode,

wherein the second communication mode is performed at a baud rate determined by the lens unit if it is determined that the lens unit is available for the second communication mode, and

wherein the second communication mode is set after a first signal notifying completion of baud rate settings is received from the lens unit.

15. A method of controlling a lens unit attachable to an imaging apparatus, that includes a first lens terminal and a second lens terminal for communication with the imaging apparatus, the method comprising:

switching between a first communication mode in which a clock signal is input via the first lens terminal and communication is performed with the imaging apparatus via the second lens terminal based on the clock signal and a second communication mode in which communication is performed with the imaging apparatus without inputting the clock signal,

determining a baud rate to be used in the second communication mode, and

transmitting a first signal notifying completion of baud rate settings to the imaging apparatus.