GS2972 Datasheet, PDF (55/125 Pages) Semtech Corporation – 3G/HD/SD-SDI Serializer with Complete SMPTE Audio & Video Support

4.7.13 Audio Word Clock
When the GS2972 combines two stereo pair inputs into one audio group, the format
allows for only one Word Clock, or sampling clock.
For the Primary group, the GS2972 uses the Word Clock associated with the source
selected by the GPA_WCLK_SRC[2:0] host interface field. If in SD mode, address 40Ch.
If in HD/3G mode, address 80Bh.
For the Secondary group, the GS2972 uses the Word Clock associated with the source
selected by the GPB_WCLK_SRC[2:0] host interface field. If in SD mode, address 40Dh.
If in HD/3G mode, address 80Ch.
For proper operation, the combined Stereo Pair inputs must have identical Word Clocks.
WCLK is not required for AES/EBU audio.
4.7.14 Channel & Group Activation
The GS2972 embeds Primary group packets when any of the following host interface
bits are set and the associated audio group enable pin is HIGH:
ACT1 Embed Primary group audio channel 1
ACT2 Embed Primary group audio channel 2
ACT3 Embed Primary group audio channel 3
ACT4 Embed Primary group audio channel 4
If none of the bits are set, then no audio will be embedded.
The GS2972 will embed Secondary group packets when any of the following host
interface bits are set and the associated audio group enable pin is HIGH:
ACT5 Embed Secondary group audio channel 1
ACT6 Embed Secondary group audio channel 2
ACT7 Embed Secondary group audio channel 3
ACT8 Embed Secondary group audio channel 4
When an embedded packet contains one or more channels with the ACTx bit set to zero,
the GS2972 replaces the data for those channels with null samples (all bits set to zero).
In the default state, the GS2972 embeds all audio channels in accordance with the
setting of the respective audio group enable pins of the device.
GS2972 3G/HD/SD-SDI Serializer with Complete
SMPTE Audio & Video Support
Final Data Sheet Rev. 9
GENDOC-047479 September 2013
www.semtech.com
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