AD1940/AD1941
Rev. B | Page 30 of 36
SERIAL OUTPUT CONTROL REGISTERS
Dither Enable (Bit 15)
Setting this bit to 1 enables dither on the appropriate channels.
Internally Link TDM Streams into Single 16-Channel Stream
(Bit 14, Serial Output Control Register 1)
When this bit is set to 1, the TDM output stream is output in a
single 16-channel stream on SDATA_OUT0. When set to 0,
TDM data is output on two independent 8-channel streams on
Pins SDATA_OUT0 and SDATA_OUT4.
Data Capture Serial Out Enable (Bit 14, Serial Output
Control Register 2)
When set to 1, SDATA_OUT7 is set as the output of the data
capture digital output registers (2640–2641). See the Data
Capture Registers section for a full explanation of this mode.
LRCLK Polarity (Bit 13)
When set to 0, the left channel data is clocked when LRCLK is
low, and the right data clocked when LRCLK is high. When set
to 1, this is reversed.
BCLK Polarity (Bit 12)
This bit controls on which edge of the bit clock the output data
is clocked. Data changes on the falling edge of BCLK_OUTx
when this bit is set to 0, and on the rising edge when this bit is
set at 1.
Master/Slave (Bit 11)
This bit sets whether the output port is a clock master or slave.
The default setting is slave; on power-up, Pins BCLK_OUTx
and LRCLK_OUTx are set as inputs until this bit is set to 1, at
which time they become clock outputs.
BCLK Frequency (Bits 10:9)
When the output port is being used as a clock master, these bits
set the frequency of the output bit clock, which is divided down
from the internal 73.728 MHz core clock.
Frame Sync Frequency (Bits 8:7)
When the output port is used as a clock master, these bits set
the frequency of the output word clock on the LRCLK_OUTx
pins, which is divided down from the internal 73.728 MHz
core clock.
Frame Sync Type (Bit 6)
This bit sets the type of signal on the LRCLK_OUTx pins.
When set to 0, the signal is a word clock with a 50% duty cycle;
when set to 1, the signal is a pulse with a duration of one bit
clock at the beginning of the data frame.
Serial Output/TDM Mode Control (Bit 5)
Setting this bit to 1 changes the output port from multiple serial
outputs to a single TDM output stream on the appropriate
SDATA_OUTx pin. This bit must be set in both serial output
control registers to enable 16-channel TDM on SDATA_OUT0.
MSB Position (Bits 4:2)
These three bits set the position of the MSB of data with respect
to the LRCLK edge. The data outputs of the AD1940/AD1941
are always MSB first.
Output Word Length (Bits 1:0)
These bits set the word length of the output data-word. All bits
following the LSB are set to 0.
Table 40. Serial Input Control Register (2646)
Register Bits Function
5 8-/16-channel TDM input
0 = Dual 8-channel TDM
1 = 16-channel TDM input
4 LRCLK polarity
0 = Frame begins on falling edge
1 = Frame begins on rising edge
3 BCLK polarity
0 = Data changes on falling edge
1 = Data changes on rising edge
2:0 Serial input mode
000 = I
2
S
001 = Left-justified
010 = TDM
011 = Right-justified, 24-bit
100 = Right-justified, 20-bit
101 = Right-justified, 18-bit
110 = Right-justified, 16-bit
SERIAL INPUT CONTROL REGISTER
8-/16-Channel TDM Input (Bit 5)
Setting this bit to 0 puts the AD1940/AD1941 into dual
8-channel TDM input mode, with the two streams coming
in on SDATA_IN2/TDM_IN1 and SDATA_IN3/TDM_IN0.
Channels 0 to 7 are input on TDM_IN0 and Channels 8 to 15
come in on TDM_IN1. Setting this bit to 1 puts the part in
16-channel TDM input mode, input on TDM_IN1.
LRCLK Polarity (Bit 4)
When set to 0, the left channel data on the SDATA_INx pins is
clocked when LRCLK_IN is low; the right input data clocked
when LRCLK_IN is high. When set to 1, this is reversed. In
TDM mode, when this bit is set to 0, data is clocked in starting
with the next appropriate BCLK edge (set in Bit 3 of this
register) that follows a falling edge on the LRCLK_IN pin.
When set to 1 and running in TDM mode, the input data is
valid on the BCLK edge following a rising edge on the word
clock (LRCLK_IN). The serial input port can also operate with
a pulse input signal, rather than a clock. In this case, the first
edge of the pulse is used by the AD1940/AD1941 to start the
data frame. When this polarity bit is set to 0, a low pulse should
be used, and a high pulse should be used when the bit it set to 1.
