DS90UA101-Q1_14 Datasheet, PDF (24/41 Pages) Texas Instruments – Multi-Channel Digital Audio Link

DS90UA101-Q1
SNLS441A – JULY 2013 – REVISED SEPTEMBER 2013
LRCK
RIGHT Channel Data
LEFT Channel Data
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BCK
DIN
MSB
210
LSB
MSB
Figure 17. Left-Justified Format
210
N
LSB
Right Justified Format
In this format, LSB of the word appears just before the LRCK edges. Left channel data word may begin at any
point depending upon the word length, but LSB of this data word must appear just before the rising edge of the
LRCK signal. Similarly, LSB of the right channel data word must appear just before falling edge of the LRCK
signal. Hence, as can be seen from below waveforms (Figure 18), data appears to be right justified.
LRCK
RIGHT Channel Data
LEFT Channel Data
BCK
DIN 0
210
MSB
LSB
MSB
Figure 18. Right-Justified Format
210
LSB
TDM Format
There are no well defined rules for TDM format and it can be implemented in large number of ways depending
upon the word length, bit clock, number of channels to be multiplexed, etc. For example, let’s assume that word
clock signal (LRCK) period = 256 * bit clock (BCK) time period. In this case, we can multiplex 4 channels with
maximum word length of 64 bits each, or 8 channels with maximum word length of 32 bits each. Figure 19
illustrates the multiplexing of 8 channels with 24 bit word length, in a format similar to I²S.
Pulse width of LRCK can be used to define a clock period for BCK or to define a slot period, i.e., the period for
which individual channel can be active on the shared data line.
If the number of audio channels is more than 8, DS90UA101-Q1/DS90UA102-Q1 can easily support multiplexed
data with additional devices to multiplex and de-multiplex the data. The number of channels multiplexed on each
data line must be selected as a power of 2, for example, 2/ 4/ 8.
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