There are two main types of serial interfaces on Blackfin that are relevant in the audio world, one is a low bit rate interface that is used for control and configuration of audio devices, and another is a higher bit rate peripheral that’s used for the actual data interchange. On the control and configuration front there are two peripherals in high usage, one is the two wire interface, the TWI, and the other is the serial peripheral interface, or SPI. In general the forward channel of these peripherals is used to configure or control an audio converter, and the reverse channel relays feedback or status information from the converter. The SPORT (what we call it on Blackfin) is a synchronous serial port and used as a data channel for audio data. It can operate at high bit rates and its full duplex supports both transmit and receive applications, and can do so simultaneously. In some codec, like the popular PC AC97, the SPORT also serves as the control channel for the codec.