14-6 Intel® PXA26x Processor Family Developer’s Manual
Inter-Integrated Circuit Sound Controller
The BITCLK, as shown in Table 14- 2, is different for different sampling frequencies. I f the
BITCLK is chosen as an output, the Audio Clock Divider Register divides the 147.46-MHz PLL
clock to generate the SYSCLK. The SYSCLK is further divided by four to generate the BITCLK.
The sampling frequency is t he fre q uency of the SYNC signal, which is ge n e ra t ed by dividing the
BITCLK by 64. See Section14.6.4, “Serial Audio Clock Divider Register (SADIV)”, for further
details about the register.
A sampling rate of 48 KH z supports MPEG2 and MP EG4. A rate of 44.1 KHz supp orts MP3.
Table 14-2. Supported Sampling Frequencies
14.5 Data Formats

14.5.1 FIFO and Memory Format

FIFO buffers are 16 words deep and 32 bits wide. This stores 32 samples per channel in each
direction.
Audio data is stored with two samples (Left + Right) per 32-bit word, ev en if samples are smaller
than 16 bits. The Left channel data occupies bits [15:0], while the Right channel data uses bits
[31:16] of the 32-bit word. Within each 16-bit field, the audio sample is left-justified, with unused
bits packed as zeroes on the right-hand (LSB) side.
In memory, the mapping of stereo samples is the sa me as in the FIFO buffers. However, single-
channel audio occupies a full 32-bit word per sample, using either the upper or lower half of the
word, depending on whether it’s considered a Left or Right sample.

14.5.2 I2S and MSB-Justified Serial Audio Formats

I2S and MSB-Justified are similar protocols for digitized stereo audi o transmitted over a serial
path.
The BITCLK supplies the serial audio bit rate, the basis for the external CODEC bit-sampling
logic. Its frequency is 64 times the audio sampling frequency. Divided by 64, the resulting 8-KHz
to 48-KHz signal signifies timing for Left and Right serial data samples passing on the serial data
paths. This Left/Right signal is sent to the CODEC on the SYNC pin. Each phase of the Left/Right
signal is accompanied by one serial audio data sample on the data pins SDATA_IN and
SDATA_OUT.
Audio Clock
Divider
Register
(31:0)
SYSCLK =
147.6MHz / (SADIV ) BITCLK =
SYSCLK / 4 SYNC or Sampling frequency =
BITCLK / 64
0x0000-000C 12.288MHz 3.072MHz 48.000 KHz (closest std = 48KHz)
0x0000-000D 11.343MHz 2.836MHz 44.308 KHz (closest std = 44.1KHz)
0x0000-001A 5.671MHz 1.418MHz 22.154 KHz (closest std = 22.05KHz)
0x0000-0024 4.096MHz 1.024 MHz 16.000KHz (closest std = 16.00 KHz)
0x0000-0034 2.836MHz 708.92 KHz 11.077KHz (closest std = 11.025KHz)
0x0000-0048 2.048MHz 512.00 KHz 8.000KHz (closest std = 8.00KHz)