CM6500B Datasheet, PDF (26/36 Pages) C-Media Electronics – USB Audio Sound Chip

CM6500 / CM6500B
USB Audio Sound Chip
Marks a word with data for channel A that isn't at the start of the data-block.
Preamble W:
Marks a word containing data for channel B. (right, for stereo). When using more than 2 channels, this could also
be any other channel (except for A).
The number of subframes that are used depends on the number of channels that is transmitted. A CD-player
uses Channels A and B (left/right) and so each frame contains two subframes. A block contains 192 frames and
starts with a preamble "B":
Sub-frame
0
34
78
Preamble Aux Data
LSB
Audio Data
27 28 29 30 31
MSB
VUCP
V:
Valid, U:User-Data, C:Channel-Status-Data, P:Parity-Bit
Figure -1 SPDIF sub-frame description
In each block, 384 bits of channel status and subcode info are transmitted. The Channel-status bits are equal
for both subframes, so actually only 192 useful bits are transmitted:
M ChannelA W ChannelA B ChannelA W ChannelA M ChannelA W ChannelA
Frame 191
SubFrame SubFrame
Frame 0
Frame 1
Figure -2 Preamble Description of 192 SPDIF frame
7.4.2 SPDIF Out Channel Status
bit0
bit1
bit2
bit3
bit4
bit5
bit6
bit7
consumer audio/
byte0
copyright
/professional non-audio
pre-emphasis
mode
default
byte1
default
byte2
default
0(P)
0(P)
0(fixed)
0(P)
1(P)
0(P)
0(fixed)
category code
0(P)
0(P)
0(P)
0(P)
source number
0(fixed) 0(fixed) 0(fixed) 0(fixed)
0(fixed) 0(fixed)
0(P)
0(P)
channel number
0(fixed) 0(fixed)
0(fixed)
L
0(P)
0(fixed)
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