GS9090 Data Sheet
The FIFO_LD_POSITION[12:0] register is designed to accommodate the longest
SD line length. If the user programs a value greater than the maximum line length
at the operating SD standard, the FIFO_LD pulse will not be generated.
After a device reset, the FIFO_LD_POSITION[12:0] register is set to zero and the
FIFO_LD pulse will assume the default timing.
3.9.2 Ancillary Data Detection and Indication
The GS9090 will detect all types of ancillary data in either the vertical or horizontal
data spaces. The ANC_DETECT status signal is provided to indicate the position
of ancillary data in the output data stream. This signal is available for output on the
multi-function output port pins, if so programmed (see Programmable
Multi-Function Outputs on page 56).
The ANC_DETECT status signal is synchronous with PCLK and can be used as a
clock enable to external logic, or as a write enable to an external FIFO or other
memory device. The ANC_DETECT signal will be asserted HIGH whenever
ancillary data is detected in the video data stream (see Figure 3-5). Both 8-bit and
10-bit ancillary data preambles will be detected by the GS9090.
NOTE 1: When the internal FIFO is configured for video mode, the ANC_DETECT
signal will be timed to the data output from the FIFO (see Video Mode on page 46).
NOTE 2: For performance in low latency mode, see GS9090 Low-latency Mode on
page 58.
PCLK
Y'CbCr DATA
DID
ANC DATA
000
3FF
DBN
3FF
DC
ANC DATA
CSUM
BLANK
ANC_DETECT
Figure 3-5: ANC_DETECT Status Signal
3.9.2.1 Programmable Ancillary Data Detection
Although the GS9090 will detect all types of ancillary data by default, it also allows
the application layer to specifically program up to five different ancillary data types
for detection. This is accomplished by setting the ANC_TYPE registers via the host
interface (see Table 3-4).
For each data type to be detected, the host interface must program the DID and/or
SDID of the ancillary data type of interest. The GS9090 will compare the received
DID and/or SDID with the programmed values and assert ANC only if an exact
match is found. The same timing shown in Figure 3-5 will be used.
28201 - 1 July 2005
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