GS2972 Datasheet, PDF (75/125 Pages) Semtech Corporation – 3G/HD/SD-SDI Serializer with Complete SMPTE Audio & Video Support

4.9.3 ANC Data Blanking
The GS2972 can blank the video input data during the H and V blanking periods. This
function will be enabled by setting the ANC_BLANK pin LOW.
This function is only available when the device is operating in SMPTE mode
(SMPTE_BYPASS = HIGH).
In this mode, input video data in the horizontal and vertical blanking periods will be
replaced by SMPTE compliant blanking values.
The blanking function will operate only on the video input signal and will remove all
ancillary data already embedded in the input video stream.
In SD mode, SAV and EAV code words already embedded in the input video stream will
be protected and will not be blanked.
In HD and 3G modes, SAV and EAV code words, line numbers and line based CRC's
already embedded in the input video stream will be protected and will not be blanked.
The above two statements are really implementation specific, and are provided only to
ensure that the “Detect TRS” function for timing generation is supported by the device,
even when the blanking function is enabled.
From a system perspective, use of the input blanking function is not recommended
unless TRS, line number and CRC generation and insertion functions are enabled.
The active image area will not be blanked.
The input blanking function will not blank any of the ancillary data, TRS words, line
numbers, CRC's, EDH, SMPTE ST 352 payload identifiers or audio control and data
packets inserted by the device itself.
4.9.4 ANC Data Checksum Calculation and Insertion
The GS2972 calculates checksums for all detected ancillary data packets and audio data
presented to the device.
ANC data checksum insertion only takes place if the IOPROC_EN/DIS pin is HIGH, the
SMPTE_BYPASS is HIGH and the ANC_CSUM_INS bit is set LOW in the IOPROC register.
Note: The device will correct any CSUM value outside the protected ranges from 000h
to 003h and from 3FCh to 3FFh. If a CSUM value in either of these ranges is presented to
the device, it will not be corrected.
4.9.5 TRS Generation and Insertion
The GS2972 is capable of generating and inserting TRS codes.
TRS word generation and insertion are performed in accordance with the timing
parameters generated by the timing circuits, which is locked to the externally provided
H:V:F or CEA-861 signals, or the TRS signals embedded in the input data stream. The
GS2972 will overwrite the TRS signals if they're already embedded. When a 3G Level A
signal is applied to the GS2972, and when the CONV_372 (bit 9 address 000h) is set LOW
(Level A to Level B conversion), TRS will be inserted according to 3G Level B format.
10-bit TRS code words are inserted at all times.
GS2972 3G/HD/SD-SDI Serializer with Complete
SMPTE Audio & Video Support
Final Data Sheet Rev. 9
GENDOC-047479 September 2013
www.semtech.com
75 of 125