adau1381 Analog Devices, Inc., adau1381 Datasheet - Page 38

• Manufacturer Part Number: adau1381
• Description: Low-noise Stereo Codec With Enhanced Recording And Playback Processing
• Manufacturer: Analog Devices, Inc.

ADAU1381
SERIAL DATA INPUT/OUTPUT PORTS
The flexible serial data input and output ports of the ADAU1381
can be set to accept or transmit data in 2-channel format or in a
4-channel or 8-channel TDM stream to interface to external ADCs
or DACs. Data is processed by default in twos complement, MSB
first format, unless otherwise configured in the control registers.
By default, the left channel data field precedes the right channel
data field in 2-channel streams. In TDM 4 mode, Slot 0 and Slot 1
are in the first half of the audio frame, and Slot 2 and Slot 3 are
in the second half of the audio frame. In TDM 8 mode, Slot 0 to
Slot 3 are in the first half of the audio frame, and Slot 4 to Slot 7
are in the second half of the frame. The serial modes and the
position of the data in the frame are set in Register 16405 (0x4015),
Serial Port Control 0; Register 16406 (0x4016), Serial Port Control 1;
Register 16407 (0x4017), Converter Control 0; and Register 16408
(0x4018), Converter Control 1.
The serial data clocks must be synchronous with the ADAU1381
master clock input. The LRCLK and BCLK pins are used to clock
both the serial input and output ports. The ADAU1381 can be
set as the master or the slave in a system. Because there is only
one set of serial data clocks, the input and output ports must
always be both master or both slave.
Register 16405 (0x4015), Serial Port Control 0, and Register
16406 (0x4016), Serial Port Control 1, allow control of clock
polarity and data input modes. The valid data formats are I
left-justified, right-justified (24-/20-/18-/16-bit), and TDM. In
all modes except for the right-justified modes, the serial port
inputs an arbitrary number of audio data bits, up to a limit of 24.
Extra bits do not cause an error, but they are truncated internally.
The serial port can operate with an arbitrary number of BCLK
transitions in each LRCLK frame.
Table 26. Data Format Configurations
Format
I
Left-Justified
Right-Justified
TDM with Clock
TDM with Pulse
2
S (see Figure 47)
(see Figure 48)
(see Figure 49)
(see Figure 50)
(see Figure 51)
Frame begins on falling edge
LRCLK Polarity
Frame begins on rising edge
Frame begins on rising edge
Frame begins on falling edge
Frame begins on rising edge
LRCLK Mode
50% duty cycle
50% duty cycle
50% duty cycle
50% duty cycle
Pulse
2
S,
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BCLK Polarity
Data changes
on falling edge
Data changes
on falling edge
Data changes
on falling edge
Data changes
on falling edge
Data changes
on falling edge
TDM MODES
The LRCLK in TDM mode can be input to the ADAU1381
either as a 50% duty cycle clock or as a bit-wide pulse.
When the LRCLK is set as a pulse, a 47 pF capacitor should be
connected between the LRCLK pin and ground, as shown
in Figure 46. This is necessary in both master and slave modes
to properly align the LRCLK signal to the serial data stream.
The ADAU1381 TDM implementation is a TDM audio stream.
Unlike a true TDM bus, its output does not become high imped-
ance during periods when it is not transmitting data.
In TDM 8 mode, the ADAU1381 can be a master for f
48 kHz. Table 25 lists the modes in which the serial output port
can function.
Table 25. Serial Output Port Master/Slave Mode Capabilities
f
48 kHz
96 kHz
Table 26 describes the proper configurations for standard audio
data formats. Right-justified modes must be configured manually
using Register 16406 (0x4016), Serial Port Control 1, Bits[7:5],
number of bit clock cycles per frame, and Bits[1:0], data delay
from LRCLK edge.
S
Figure 46. TDM Pulse Mode LRCLK Capacitor Alignment
2-Channel Modes (I
Justified, Right-Justified)
Master and slave
Master and slave
BCLK Cycles/
Audio Frame
64
64
64
64 to 256
64 to 256
47pF
ADAU1381
LRCLK
BCLK
2
S, Left-
Data Delay from
LRCLK Edge
Delayed from LRCLK edge
by 1 BCLK
Aligned with LRCLK edge
Delayed from LRCLK edge
by 8, 12, or 16 BCLKs to
align LSB with right edge
of frame.
Delayed from start of word
clock by 1 BCLK
Delayed from start of word
clock by 1 BCLK
8-Channel TDM
Master and slave
Slave
S
up to