Data Sheet ADAU1462/ADAU1466
Rev. C | Page 65 of 202
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 42.
Table 42. 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 67), 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 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
SERIAL AUDIO
INPUT STREAM
8-BIT DATA
24-BIT
AUDIO
SAMPLE
8-BIT DATA
LSB
MSB MSB
DSP CORE
AUDIO LSB
AUDIO MSB
AUDIO LSB
AUDIO MSB
AUDIO LSB
AUDIO MSB
14810-065
Figure 67. 32-Bit Serial Input Example
In 24-bit mode (see Figure 69), 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 7 sign-extended zeros on top,
1 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 8 zeros (in the 24-bit
case). The resulting 8.24 sample, therefore, has 7 sign-extended
zeros on top, 9 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 43).
Table 43. 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 68), 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 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
32-BIT
SERIAL AUDIO
OUTPUT STREAM
AUDIO LSB
AUDIO MSB
AUDIO LSB
AUDIO MSB
AUDIO LSB
AUDIO MSB
14810-066
Figure 68. 32-Bit Serial Output Example
In 24-bit mode, the top 7 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 8 zeros padded under the LSB (see
Figure 70).
In 16-bit mode, the top 7 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 8 LSBs. The resulting
1.15 word is then zero padded with 16 zeros under the LSB and
output from the serial port.