Intel® PXA26x Processor Family Developer’s Manual 14-1
Inter-Integrated Circuit Sound Controller 14
Inter-Integrated Circuit Sound (I2S) is a protocol for digital stereo audio. The I2S controller (I2SC)
functional block for the Intel® PXA26x Processor Family controls the I2S link (I2SLINK), which
is a low-power four-pin serial interface for stereo audio. The I2S interface, the Audio CODEC ‘97
(AC’97) interface, and the ASSP may not be used at the same time.

14.1 Overview

The I2S controller consists of buffers, status and control registers, serializers, and counters for
transferring digitized audio between the processor system memory and an exter nal I2S CODEC.
For playback of digitized audio or production of synthesized audio, the I2SC retrieves digitized
audio samples from processor system memory an d sends them to a CODEC through the I2SLINK.
The external digital-to-analog converter in the CODEC then converts the audio samples into an
analog audio waveform.
For recording of digitized audio, the I2SC receives digitized audio samples fr om a CODEC
(through the I2SLINK) and stores them in processor system memory.
The I2S controller supports the normal-I2S and the MSB-Justified-I2S formats. Four, or optionally
five, pins connect the controller to an external CODEC:
A bit-rate clock, which can use either an internal or an external source.
A formatting or “Left/Right” control signal.
Two serial audio pins, one input and one output.
The bit-rate clock, an optional system clock also sent to the CODEC by the I2SC.
The I2S data can be stored to and retrieved from system memory either by the DMA controller or
by programmed I/O.
For I2S systems, additional pins are required to control the external CODEC. Some CODECs use
an L3 control bus, which requires 3 signals — L3_CLK, L3_DATA, and L3_MODE — for writing
bytes into the L3-bus register. The I2SC supports the L3 bus protocol v ia software control of the
general-purpose I/O (GPIO) pins. The I2SC does not provide hardware control for the L3 bus
protocol.
Two similar protocols exist for transmitting digitized stereo audio over a serial path: Normal-I2S
and MSB-Justified-I2S. Both work with a variety of clock rates, which can be obtained by dividing
the PLL clock by a programmable divider, or from an external clock source. For further details
regarding clock rates, see Table14-2, “Supported Sampling Frequencies” on page14-6.