Interface circuit and information processing system for detecting a connection state based on a notification received through a hot plug detect line

An information processing system, comprising:

• a first apparatus;
• and
• a second apparatus, wherein
• the first apparatus is configured to communicate with the second apparatus via a High-Definition Multimedia Interface (HDMI) cable,
• the first apparatus comprises:
• receiving circuitry configured to:
• receive a first signal by a differential signal from the second apparatus through a pair of a utility line and a Hot Plug Detect (HPD) line of the HDMI cable, wherein the first signal includes a first clock component and an audio signal;
• receive a second signal by an in-phase signal from the second apparatus through the pair of the utility line and the HPD line, wherein the second signal includes a second clock component;
• and
• receive a notification of a connection state of the second apparatus from the second apparatus through the HPD line, and processing circuitry configured to process the audio signal, and
• the second apparatus comprises:
• transmission circuitry configured to:
• transmit the first signal by the differential signal to the first apparatus through the pair of the utility line and the HPD line;
• transmit the second signal by the in-phase signal to the first apparatus through the pair of the utility line and the HPD line;
• and
• notify the first apparatus of the connection state of the second apparatus through the HPD line.