ADSP-214xx SHARC Processor Hardware Reference 13-17
Sony/Philips Digital Interface
detected, the
DIR_NOAUDIO bit flag is set. If the sync code is not detected
again within 4096 frames, the DIR_NOAUDIO bit flag is deasserted.
The last two words of the sync code, 0xF872 and 0x4E1F, are called the
preamble-A and preamble-B of the burst preamble. Preamble-C of the
burst preamble contains burst information and is captured and stored by
the receiver. Preamble-D of the burst preamble contains the length code
and is captured by the receiver. Even if the validity bit or bit 1 of byte 0
has been set, the receiver still looks for the sync code in order to record the
preamble-C and D values. Once the sync code has not been detected in
4096 frames, the preamble-C and D registers are set to zero.
The S/PDIF receiver in 2147x and 2148x, supports all DTS frame
sizes of 256, 512, 1024, 2048 and 4096. To enable support for
2048 and 4096 DTS frame sizes, DTS_CD_4K_EN bit in
DIRCTL, need to be set. In 2146x on-chip S/PDIF receiver sup-
ports 256, 512 and 1024 DTS frames only. The DTS test kit
frames with 2048 and 4096 frame sizes can be detected by adding
the sync detection logic in software by using a software counter to
check for the DTS header every 2048 and 4096 frames
respectively.
Emphasized Audio Data
The receiver must indicate to the program whether the received audio data
is emphasized using the channel status bits as detailed below.
• In professional mode, (bit 0 of byte 0 = 1), channel status bits 2–4
of byte 0 indicate the audio data is emphasized if they are equal to
110 or 111.
• In consumer mode, (bit 0 of byte 0 = 0), channel status bits 3–5
indicate the audio data is emphasized if they are equal to 100, 010
or 110.
If emphasis is indicated in the channel status bits, the receiver asserts the
EMPHASIS bit flag. This bit flag is used to generate an interrupt.
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