A host communication circuit that is adapted to be connected to a client communication circuit by means of a clock wire (CLKW), a selection wire (SELW), a first data wire and a second data wire, the host communication circuit being configured - to transmit a digital selection signal over the selection wire (SELW) to the client communication circuit, the selection signal determining whether either an audio transmission mode or a client communication mode is selected; - to transmit digital audio data of a first channel and a second channel over the first and the second data wire (DW1, DW2) to the client communication circuit in the audio transmission mode, and to perform client communication over the first and the second data wire (DW1, DW2) in the client communication mode; - when performing client communication in the client communication mode, to transmit a direction indicator (R/W); - to transmit a first bit sequence over the first data wire to the client communication circuit, wherein, in the audio transmission mode, the first bit sequence comprises the audio data of the first channel, and, when performing client communication, the first bit sequence comprises index data; - in the audio transmission mode, to transmit a second bit sequence over the second data wire to the client communication circuit, wherein the second bit sequence comprises the audio data of the second channel; - when performing client communication, if the direction indicator (R/W) is associated with a write mode, to transmit a second bit sequence over the second data wire to the client communication circuit, wherein the second bit sequence comprises payload data; and - when performing client communication, if the direction indicator (R/W) is associated with a read mode, to receive a second bit sequence over the second data wire from the client communication circuit, wherein the second bit sequence comprises payload data. - to transmit a digital selection signal over the selection wire (SELW) to the client communication circuit, the selection signal determining whether either an audio transmission mode or a client communication mode is selected; - to transmit digital audio data of a first channel and a second channel over the first and the second data wire (DW1, DW2) to the client communication circuit in the audio transmission mode, and to perform client communication over the first and the second data wire (DW1, DW2) in the client communication mode; - when performing client communication in the client communication mode, to transmit a direction indicator (R/W); - to transmit a first bit sequence over the first data wire to the client communication circuit, wherein, in the audio transmission mode, the first bit sequence comprises the audio data of the first channel, and, when performing client communication, the first bit sequence comprises index data; - in the audio transmission mode, to transmit a second bit sequence over the second data wire to the client communication circuit, wherein the second bit sequence comprises the audio data of the second channel; - when performing client communication, if the direction indicator (R/W) is associated with a write mode, to transmit a second bit sequence over the second data wire to the client communication circuit, wherein the second bit sequence comprises payload data; and - when performing client communication, if the direction indicator (R/W) is associated with a read mode, to receive a second bit sequence over the second data wire from the client communication circuit, wherein the second bit sequence comprises payload data.