ADSP-214xx SHARC Processor Hardware Reference 10-37
Serial Ports
Companding Limitations (ADSP-2146x)
In multichannel mode there is an option to enable companding for any
active channel. If the first active channel is NOT the channel 0 and com-
panding is enabled for the first active channel (channel 2), then from the
second frame onward companding for the first active channel (channel 2)
does not occur. In Table 10-9, x = Don’t care 0 = Not Active 1 = Active.
In Table 10-9 channel 0 and 1 are not active and channel 2 is active and
companding is enabled. In the first frame companding occurs for the first
active channel (channel 2) but the second frame onward companding for
the first active channel (channel 2) does not occur. However, for other
channels, companding occurs correctly.
Packed Mode
A packed mode is available in the SPORT and used for audio codec com-
munications using multiples channels. This mode allows applications to
send more than the standard 32 bits per channel available through stan-
dard I
2
S mode. Packed mode is implemented using standard multichannel
mode (and is therefore programmed similarly to multichannel mode).
Packed mode also supports the maximum of 128 channels as does multi-
channel mode as well as the maximum of (128 x 32) bits per left or right
channel.
As shown in Figure 10-9, packed waveforms are the same as the wave
forms used in multichannel mode, except that the frame sync is toggled
Table 10-9. Companding
Channel Number 012345
Active Channel Number 0 0 1 x x x
Companding Enable 0 0 1 x x x
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