EVAL-AD1940EB View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-AD1940EB' PDF : 32 Pages View PDF
BCLK Polarity (Bit 3)
This bit controls on which edge of the bit clock the input data
changes, and on which edge it is clocked. Data changes on the
falling edge of BCLK_IN when this bit is set to 0, and on the
rising edge when this bit is set at 1.
Serial Input Mode (Bits 2:0)
These two bits control the data format that the input port
expects to receive. Bits 3 and 4 of this control register override
the settings in Bits 2:0, so all four bits must be changed together
for proper operation in some modes. The clock diagrams for
these modes are shown in Figure 23, Figure 24, and Figure 25.
Note that for left-justified and right-justified modes the LRCLK
polarity is high, then low, which is opposite from the default
setting of Bit 4.
When these bits are set to accept a TDM input, the AD1940/
AD1941’s data starts after the edge defined by Bit 4. Figure 26
shows an 8-channel TDM stream with a high-to-low triggered
LRCLK and data changing on the falling edge of the BCLK. The
AD1940/AD1941
AD1940/AD1941 expects the MSB of each data slot delayed by
one BCLK from the beginning of the slot, just like in the stereo
I2S format. In 8-channel TDM mode, Channels 0 to 3 are in the
first half of the frame, and Channels 4 to 7 are in the second
half. When in 16-channel TDM mode, the first half-frame holds
Channels 0 to 7, and the second half-frame holds Channels 8 to
15. Figure 26 shows just one of the formats in which the
AD1940/AD1941 can operate in TDM mode. Please refer to the
Serial Data Input/Output Ports section for a more complete
description of the modes of operation. Figure 27 shows an
example of a TDM stream running with a pulse word clock,
which would be used to interface to ADI codecs in their
auxiliary mode. To work in this mode on either the input or
output serial ports, the AD1940/AD1941 should be set to frame
beginning on the rising edge of LRCLK, data changing on the
falling edge of BCLK, and MSB position delayed from the start
of the word clock by one BCLK.
Table 37 explains the clock settings for each of these formats.
LRCLK
BCLK
SDATA
LEFT CHANNEL
RIGHT CHANNEL
MSB
LSB
MSB
LSB
1 /FS
Figure 23. I2S Mode—16 to 24 Bits per Channel
LRCLK
BCLK
SDATA
MSB
LEFT CHANNEL
RIGHT CHANNEL
LSB
MSB
1 /FS
LSB
Figure 24. Left-Justified Mode—16 to 24 Bits per Channel
LRCLK
BCLK
SDATA
LEFT CHANNEL
RIGHT CHANNEL
MSB
LSB
1 /FS
MSB
LSB
Figure 25. Right-Justified Mode—16 to 24 Bits per Channel
Rev. A | Page 31 of 36
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