I
2
S Mode
C-4
ADSP-214xx SHARC Processor Hardware Reference
The I
2
S bus transmits audio data from 8–32 bits and control signals over
separate lines. The data line carries two multiplexed data channels—the
left channel and the right channel. In I
2
S mode, if both channels on a
SPORT are set up to transmit, then the SPORT transmits left and right
I
2
S channels simultaneously. If both channels on a SPORT are set up to
receive, the SPORT receives left and right I
2
S channels simultaneously.
Data is transmitted in MSB-first format.
I
2
S consists, as stated above, of a bit clock, a word select and the data line.
The bit clock pulses once for each discrete bit of data on the data lines.
The bit clock operates at a frequency which is a multiple of the sample
rate. The bit clock frequency multiplier depends on number of bits per
channel, times the number of channels. For example, CD Audio with a
sample frequency of 44.1 kHz and 32 bits of precision per (2) stereo chan-
nels has a bit clock frequency of 2.8224 MHz. The word select clock lets
the device know whether channel 1 or channel 2 is currently being sent,
since I
2
S allows two channels to be sent on the same data line.
Transitions on the word select clock also serve as a start-of-word indicator.
The word clock line pulses once per sample, so while the bit clock runs at
some multiple of the sample frequency, the word clock always matches the
sample frequency. For a two channel (stereo) system, the word clock is a
square wave, with an equal number of bit clock pulses clocking the data to
each channel. In a mono system, the word clock pulses one bit clock
length to signal the start of the next word, but is no longer be square.
Instead, bit clocking transitions occur with the word clock either high or
low.
Note the major difference between I
2
S and left/right justified modes is a
left MSB data shift by one
SCLK
cycle in relation to the frame.
Standard I
2
S data is sent from MSB to LSB, starting at the left edge of the
word select clock, with one bit clock delay. This allows both the transmit-
ting and receiving devices to ignore the audio precision of the remote
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Содержание SHARC ADSP-214 Series
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Страница 72: ...Notation Conventions lxxii ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 130: ...Programming Model 2 52 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 264: ...Programming Models 3 134 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 290: ...Programming Model 4 26 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 296: ...Programming Model 5 6 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 396: ...Effect Latency 7 28 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 520: ...Programming Model 10 62 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 616: ...Debug Features 14 22 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 656: ...Programming Model 15 40 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 714: ...Programming Model 19 10 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 1132: ...Register Listing A 306 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 1192: ...Index I 34 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...