Image-capturing apparatus, accessory apparatus, and control method therefor with changing signal level of communication channel from one level to another

摘要

The image-capturing apparatus communicates with an accessory apparatus using a clock/communication request channel and first and second data communication channels. The camera controller switches its communication method between a first communication method in which data communication is performed while a clock signal is alternately switched between first and second levels and a second communication method in which data communication is performed in response to a communication request from the camera controller to the accessory apparatus, which is output by switching a signal level of the clock/communication request channel from the first level to the second level. The camera controller, in response to detecting a communication error in the first and second communication methods, transmits to the accessory apparatus through the second data communication channel a specific signal for restoring the communication while keeping the signal level of the clock/communication request channel at the first level.