Cirrus Logic CS4970x4 - Manual (Page 77)

Digital Audio Output Port Description
CS4953x4/CS4970x4 System Designer’s Guide
DS810UM6 Copyright 2013 Cirrus Logic, Inc 4-3
4.2.2 Supported DAO Functional Blocks
As mentioned earlier in the previous section, two DAO ports, DAO1_DATA3 and DAO2_DATA3, are
unique in that they are designed to serve as either an output for I
2
S or left-justified PCM data or as S/PDIF
transmitters (XMTA and XMTB). When configured as S/PDIF transmitters, the ports encode digital audio
data according to the Sony
®
/Philips
®
Digital Interface Format (S/PDIF), also known as IEC60958, or the
AES/EBU interface format. Please see Figure 4-1 for a block diagram of the supported functional blocks
for the DAO on the CS4953x4/CS4970x4
4.2.3 DAO Interface Formats
The DAO interface has 8 stereo data outputs that are fully configurable including support for I
2
S, left-
justified, and multichannel (one-line data mode) formats. This section describes some common audio
formats that the CS4953x4/CS4970x4 DAO interface supports. It should be noted that the digital output
ports provide up to 32-bit PCM resolution.
Note: DAO1_DATAx is valid with respect to DAO1_SCLK/DAO1_LRCK and DAO2_DATAx is valid
with respect to DAO2_SCLK/DAO2_LRCK.
4.2.3.1 I
2
S Format
In this format, data is presented most-significant bit (MSB) first, one DAO_SCLK delay after the transition
of DAO_LRCLK, and is valid on the rising edge of DAO_SCLK. The left subframe is presented when
DAO_LRCLK is low, and the right subframe is presented when DAO_LRCLK is high.
Figure 4-2 provides
details on I
2
S compatible (maximum of 32 bits) serial audio formats.
Figure 4-2. I 2 S Compatible Serial Audio Formats (Rising Edge Valid
4.2.3.2 Left-Justified Format
Figure 4-3 illustrates the left-justified (LJ) format with a rising edge DAO_SCLK. Data is presented most-
significant bit first on the first DAO_SCLK after a DAO_LRCLK transition and is valid on the rising edge of
DAO_SCLK. The left subframe is presented when DAO_LRCLK is high and the right subframe is
presented when DAO_LRCLK is low. This format can also be programmed for data to be valid on the
falling edge of DAO_SCLK.
Figure 4-3. Left-justified Digital Audio Formats (Rising Edge Valid DAO_SCLK)
DAO_LRCLK
DAO_SCLK
Left Channel Right Channel
DAO_DATA +3 +2 +1 LSB +5 +4 MSB-1 -2 -3 -4 -5 +3 +2 +1 LSB +5 +4 MSB-1 -2 -3 -4
DAO_LRCLK
DAO_SCLK
L e ft C h a n n e l R i g h t C h a n n e l
DAO_DATA +3 +2 +1 LSB +5 +4 MSB -1 -2 -3 -4 -5 +3 +2 +1 +5 +4 -1 -2 -3 -4 LSB MSB