Data Sheet ADAU1452/ADAU1451/ADAU1450
Serial Input Ports
There is a one-to-one mapping between the serial input ports
and the audio input channels in the DSP and the ASRC input
selectors, which is described in Table 47.
Table 47. Relationship Between Serial Input Port and
Corresponding Channel Numbers on the DSP and ASRC Inputs
Serial Port Audio Input Channels in the DSP and ASRC
Serial Input 0 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
Serial Input 1 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30,
31
Serial Input 2 32, 33, 34, 35, 36, 37, 38, 39
Serial Input 3 40, 41, 42, 43, 44, 45, 46, 47
If a serial input port is configured using the SERIAL_BYTE_x_0
registers, Bits[2:0] (TDM_MODE) for a number of channels that
is less than its maximum channel count, the unused channels carry
zero data. For example, if Serial Input 0 is set in 8-channel (TDM8)
mode, the first eight channels (Channel 0 to Channel 7) carry data;
and the unused channels (Channel 8 to Channel 15) carry no data.
There are four options for the word length of each serial input port:
24 bits, 16 bits, 32 bits, or flexible TDM. The flexible TDM option
is described in the Flexible TDM Input section.
In 32-bit mode (see Figure 66), the 32 bits received on the serial
input are mapped directly to a 32-bit word in the DSP core. To
use 32-bit mode, the special 32-bit input cells must be used in
SigmaStudio.
24-BIT
AUDIO
SAMPLE
8-BIT DATA
ROUTING
MATRIX
24-BIT
AUDIO
SAMPLE
LSB
32-BIT
INPUT PORT
32-BIT
SERIALAUDIO
INPUT STREAM
8-BIT DAT A
24-BIT
AUDIO
SAMPLE
8-BIT DAT A LSB
MSB MSB
DSP CORE
11486-069
AUDIO LSB
AUDIO M S B
AUDIO LSB
AUDIO M S B
AUDIO LSB
AUDIO M S B
Figure 66. 32-Bit Serial Input Example
In 24-bit mode (see Figure 68), the 24-bit audio sample (in 1.23
format) is padded with eight zeros below its LSB (in 1.31 format) as
it is input to the routing matrix. Then, the audio data is shifted
such that the audio sample has seven sign-extended zeros on
top, one padded zero on the bottom, and 24 bits of data in the
middle (8.24 format).
Whereas 16-bit mode is similar to 24-bit mode, the 16-bit audio
data has 16 zeros below its LSB instead of just eight zeros (in the
24-bit case). The resulting 8.24 sample, therefore, has seven
sign-extended zeros on top, nine padded zeros on the bottom,
and 16 bits of data in the middle (8.24 format).
Serial Output Ports
There is a one-to-one mapping between the serial output ports
and the output audio channels in the DSP (see Table 48).
Table 48. Relationship Between Serial Input Port and
Corresponding DSP Output Channel Numbers
Serial Input Port Audio Output Channels from the DSP
Serial Output 0 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
Serial Output 1 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27,
28, 29, 30, 31
Serial Output 2 32, 33, 34, 35, 36, 37, 38, 39
Serial Output 3 40, 41, 42, 43, 44, 45, 46, 47
If a serial output port is configured using the SERIAL_BYTE_x_0
registers, Bits[2:0] (TDM_MODE), for a number of channels that
is less than its maximum channel count, the unused channels
are ignored. For example, if Serial Output Port 0 is set in 8-channel
(TDM8) mode, and data is routed to it from the DSP, the first
eight DSP output channels (Channel 0 through Channel 7) are
output on SDATA_OUT0, but the remaining channels (Channel 8
through Channel 15) are not output from the device.
There are four options for the word length of each serial output
port: 24 bits, 16 bits, 32 bits, or flexible TDM. See the Flexible
TDM Output section for more information.
In 32-bit mode (see Figure 67), all 32 bits from the 8.24 word in
the DSP core are copied directly to the serial output. To use 32-bit
mode, the special 32-bit output cells must be used in SigmaStudio.
ROUTING
MATRIX
32-BIT
WORD 32-BIT
WORD 32-BIT
WORD
32-BIT
OUTPUT PORT
LSB
MSB
11486-071
32-BIT
SERIAL AUDIO
OUT P UT STREAM
AUDIO LSB
AUDIO M S B
AUDIO LSB
AUDIO M S B
AUDIO LSB
AUDIO M S B
Figure 67. 32-Bit Serial Output Example
In 24-bit mode, the top seven MSBs of the 8.24 audio word in
the DSP core are saturated, and the resulting 1.23 word is output
from the serial port, with eight zeros padded under the LSB (see
Figure 69).
In 16-bit mode, the top seven MSBs of the 8.24 audio word in
the DSP core are saturated, and the resulting 1.23 word is then
truncated to a 1.15 word by removing the eight LSBs. The
resulting 1.15 word is then zero padded with 16 zeros under the
LSB and output from the serial port.
Rev. C | Page 61 of 180