
Data Sheet
ADAU1442/ADAU1445/ADAU1446
Rev. D | Page 31 of 92
SERIAL DATA INPUT/OUTPUT
The flexible serial data input and output ports of th
e ADAU1442/a 2-channel (usually I2S format), packed TDM4, or standard 4-, 8-,
or 16-channel TDM stream. Data is processed in twos complement,
MSB-first format. The left-channel data field always precedes the
right-channel data field in 2-channel streams. In the TDMn modes
(where n represents the total number of channels in the stream),
Slot 0 to Slot (n/2) 1 fall in the first half of the audio frame, and
Slot n/2 to Slot n 1 are in the second half of the frame. TDM
mode allows fewer serial data pins to be used, freeing more pins
for other data streams. The serial modes are set in the serial output
port modes and serial input port modes control registers.
When referring to audio data streams, the terms TDM2 and I2S
should be treated with care. In this document, TDM2 refers to
any 2-channel stream, whereas I2
S refers specifically to a 2-channel,
negative BCLK polarity, negative LRCLK polarity, MSB delay-
by-1 stream.
The serial data clocks are fully bidirectional and do not need to
master clock input. However, asynchronous data streams must
be routed through an on-board asynchronous sample rate
converter to be processed in the core.
The input control registers allow control of clock polarity and data
input modes. All common data formats are available with flexible
MSB start, bit depth (24-, 20-, or 16-bit), and TDM settings. In all
modes except the right-justified modes, the serial port accepts an
arbitrary number of bits up to a limit of 24. Extra bits do not
cause an error, but they are truncated internally. Proper operation
of the right-justified modes requires that there be exactly 64 BCLKs
per audio frame (for 2-channel data). The LRCLK in TDM mode
a 50/50 duty cycle clock or as a bit-wide pulse.
In TDM mode, the bit clock supplied by the
ADAU1442/This, in turn, limits the sampling rate at which it can supply
master clocks in various TDM modes.
Table 18 displays the
modes in which the serial output port functions for some
common audio sample rates.
The output control registers give the user control of clock polarities,
clock frequencies, clock types, and data format. In all modes except
the right-justified modes (MSB delayed by 8, 12, or 16), the serial
port accepts an arbitrary number of bits up to a limit of 24.
Extra bits do not cause an error, but are truncated internally.
Proper operation of the right-justified modes requires the LSB
to align with the edge of the LRCLK. The default settings of all
serial port control registers correspond to 2-channel, I2S mode,
and 24-bit slave mode, and these registers are set as slaves to the
clock domain corresponding to their channel number.
Table 18. Serial Input and Output Port TDM Capabilities
Mode
BCLK Cycles
per Frame
fS (kHz)
BCLK
Frequency (MHz)
Valid
Mode
TDM2
64
44.1
2.8224
Yes
64
48
3.072
Yes
64
88.2
5.6448
Yes
64
96
6.144
Yes
64
192
12.288
Yes
TDM4
128
44.1
5.6448
Yes
128
48
6.144
Yes
128
88.2
11.2896
Yes
128
96
12.288
Yes
128
192
24.576
Yes
TDM8
256
44.1
11.2896
Yes
256
48
12.288
Yes
256
88.2
22.5792
Yes
256
96
24.576
Yes
256
192
49.152
TDM16
512
44.1
22.5792
Yes
512
48
24.576
Yes
512
88.2
45.1584
512
96
49.152
512
192
98.304
1
The device will not work in this mode.
Connections to an external DAC are handled exclusively with
the output port pins. The output LRCLKx and BCLKx pins can
be set to be either master or slave, and the SDATA_OUT pins
are used to output data from the SigmaDSP to the external DAC.
Table 19 shows the proper configurations for standard audio
data input/output ports.