CS4226_04 Datasheet, PDF (17/37 Pages) Cirrus Logic – Surround Sound Codec

CS4226
2.5.3 Auxiliary Audio Port Signals
The auxiliary port provides an alternate way to
input digital audio signals into the CS4226,
and allows the CS4226 to synchronize the
system to an external digital audio source.
This port consists of serial clock, data and
left/right clock pins named, SCLKAUX, DA-
TAUX and LRCKAUX. The Auxiliary Audio
Port input is output on SDOUT1 when the IS
bits are set to 1 or 2 in the ADC Control Byte.
Additionally, setting IS to 2 routes the stereo
ADC outputs to SDOUT2. There is approxi-
mately a two frame delay from DATAUX to
SDOUT1. When the auxiliary port is used, the
frequency of LRCKAUX must equal to the sys-
tem sample rate, Fs, but no particular phase
relationship is required.
De-emphasis and muting on error conditions
can be performed on input data to the auxiliary
audio port; this is controlled by the Auxiliary
Port Control Byte.
2.5.4 Auxiliary Audio Port Formats
Data input on DATAUX is clocked into the part
by SCLKAUX using the format selected in the
Auxiliary Port Mode Byte. The auxiliary audio
port supports the same 5 formats as the audio
DSP port in multi-data line mode. LRCKAUX is
used to indicate left and right data samples,
and the start of a new sample period.
SCLKAUX and LRCKAUX may be output from
the CS4226, or they may be generated from
an external source, as set by the AMS1/0 con-
trol bits in the Auxiliary Port Mode Byte.
2.5.5 S/PDIF Receiver
The CS4226 reconfigures its auxiliary digital
audio port as an S/PDIF receiver if CS2/1/0 in
the Clock Mode Byte are set to be 4, 5, 6, or 7.
In this mode RX1, RX2, RX3, or RX4 can be
chosen as the S/PDIF input source.
The PLL will lock to the requested data source
and setting IS1/0 = 1 or 2 in the ADC Control
Byte routes the recovered output to SDOUT1
(channel A to left, channel B to right). All 24 re-
ceived data bits will pass through the part to
SDOUT1 except when the serial port is config-
ured with 32 SCLKs per frame or in Format 5.
For these cases, the 16 or 20 MSBs respec-
tively will be output.
The error flags are reported in the Receiver
Status Byte. The LOCK bit indicates whether
the PLL is locked to the incoming S/PDIF data.
Parity, Biphase, or Validity errors (PAR=1,
BIP=1 or V=1) will cause the last valid data
sample to be held at the receiver input until the
error condition no longer is present (see Hold
section). Mute on extended hold can also be
enabled through the Auxiliary Port Control
Byte (see Hold section).
Other error flags include confidence, CONF,
and cyclic redundancy check, CRC. The
CONF flag occurs when the received data eye
opening is less than half a bit period. This indi-
cates that the quality of the transmission link is
poor and does not meet the digital audio inter-
face standards. The CRC flag is updated at the
beginning of a channel status block and is only
valid when the professional format of channel
status data is received. This error indicates
when the CS4226 calculated CRC value does
not match the CRC byte of the received chan-
nel status block.
The OVL/ERR pin will go high to flag an error.
It is a latched logical OR of the Parity, Biphase,
Validity, and Lock error flags in the Receiver
Status Byte which is reset at the end of each
frame. However, Parity, Biphase, or Validity
errors can be masked from the pin by clearing
the PM, BM, and VM bits respectively, of the
Input Control Byte.
DS188F4
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