Cirrus Logic CS485xx - Manual (Page 70)

Digital Audio Output Port Description
CS485xx Hardware User’s Manual
DS734UM7 Copyright 2009 Cirrus Logic, Inc. 6-4
6.2.2 Supported DAO Functional Blocks
As mentioned in Section 6.1 , DAO_DATA3 on CS48560 is unique in that it is designed to serve as either an
output for I
2
S or left-justified PCM data or as a S/PDIF transmitter (XMTA). On the CS48540 and CS48520 it
is only a s S/PDIF transmitter (XMTA). When configured as a S/PDIF transmitter, it encodes digital audio
data according to the Sony/Phillips Digital Interface Format (S/PDIF), also known as IEC60958, or the AES/
EBU interface format.
6.2.3 DAO Interface Formats
The DAO interface has up to 6 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 CS485xx DAO interface supports. It should be noted that the digital output ports provide up
to 32-bit PCM resolution.
6.2.3.1 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 6-4 provides
details on I
2
S compatible (maximum of 32 bits) serial audio formats.
Figure 6-4. I
2
S Compatible Serial Audio Formats (Rising Edge Valid DAO_SCLK)
6.2.3.2 Left-Justified Format
Figure 6-5 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 6-5. 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 ht C h a n n el
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