GS2970 Datasheet, PDF (73/145 Pages) Semtech Corporation – 3Gb/s, HD, SD SDI Receiver Complete with SMPTE Audio and Video Processing

programmed (with the other set to zero), ancillary data packets are extracted from one
line per frame only. When both registers are set to zero, the device extracts packets from
all lines.
To start Ancillary Data Extraction, the ANC_DATA_EXT_MASK bit of the host interface
must be set LOW. Ancillary data packet extraction begins in the following frame (see
Figure 4-29: Ancillary Data Extraction - Step A).
Application Layer
Read Pointer
Internal Write
Pointer
Bank A
0 ANCDATA
ANC DATA
ANC DATA
ANC DATA
ANC DATA
ANC DATA
ANC DATA
800h
Bank B
0
800h
1023
BFFh
1023
BFFh
ANC_DATA_SWITCH = LOW
Figure 4-29: Ancillary Data Extraction - Step A
Ancillary data is written into Bank A until full. The Y/1ANC and C/2ANC output flags
can be used to determine the length of the ancillary data extracted and when to begin
reading the extracted data from memory.
While the ANC_DATA_EXT_MASK bit is set LOW, the ANC_DATA_SWITCH bit can be
set HIGH during or after reading the extracted data. New data is then written into Bank
B (up to 1024 x 16-bit words), at the corresponding host interface addresses (see Figure
4-30: Ancillary Data Extraction - Step B).
GS2970 3Gb/s, HD, SD SDI Receiver Complete with
SMPTE Audio and Video Processing
Data Sheet
47478 - 4
September 2012
73 of 145