The I2S serial sound bus
The I2S is a particular application of the PCM serial interface described above. It is designed to handle audio data between different devices such as compact disc players, digital recorders and digital television. The bus (Figure 18.13) has three lines:
● serial data (SD)
● word select (WS)
● continuous serial clock (SCK)
The device generating SCK and WS is known as the master.
Serial data is transmitted in two’s compliment with the MSB first to avoid incompatibility of word lengths between the transmitter and the receiver. Time-division multiplexing is used to send alternate channels, L, R, L as shown in Figure 18.14. The WS line indicates the channel being transmitted as follows:
● WS low (logic 0) channel 1 (left)
● WS high (logic 1) channel 2 (right).
WS may change either on the trailing or leading edge of the serial clock, but it does not need to be symmetrical.