GS1500 Gennum Corporation, GS1500 Datasheet - Page 10

• Manufacturer Part Number: GS1500
• Description: Hd-linx (tm) THDTV Serial Digital Deformatter With Anc Fifos
• Manufacturer: Gennum Corporation

3. DETAILED DESCRIPTION
3. DETAILED DESCRIPTION
3. DETAILED DESCRIPTION
3. DETAILED DESCRIPTION
3.1 DATA INPUT AND OUTPUTS
Data enters and exits the device on the rising edge of
PCLK_IN as shown in Figures 1 and 2. This data can be
scrambled or unscrambled and framed or unframed.
3.2 DESCRAMBLER AND FRAMER
Both the descrambler and framer can be enabled or
disabled independently to allow the input to remain
scrambled or unscrambled. If the data is unscrambled, it
can be word aligned (framed) or pass through unaltered.
3.3 STANDARDS INDICATION
VD_STD[3:0] indicates the standard that the device has
detected. The states of VD_STD[3:0] are shown Tables 1
and 2.
TABLE 1: Progressive Scan Standards Indication (VD_STD[3]=0)
TABLE 2: Interlaced Standards Indication (VD_STD[3]=1)
Note the following in the above Standards Indication Tables:
•
•
•
•
See Table 3 for more details on the source format
parameters.
GENNUM CORPORATION
VD_STD[3:0]
VD_STD[3:0]
SMPTE260M is 1125 lines/frame
SMPTE274M is 1125 lines/frame
SMPTE295M is 1250 lines/frame
SMPTE296M is 750 lines/frame
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
720p (60 & 60/1.001Hz → L/M) [SMPTE296M]
Reserved
1080p (30 & 30/1.001Hz → G/H)
[SMPTE274M]
Reserved
1080p (25Hz → I) [SMPTE274M]
Reserved
1080p (24 & 24/1.001Hz → J/K) [SMPTE274M]
Unknown Progressive with F = 0 always.
1080i (30 & 30/1.001Hz → D/E) [SMPTE274M]
Reserved
1080i (25Hz → F) [SMPTE274M]
Reserved
1080i (25Hz → C) [SMPTE295M]
Reserved
1035i (30 & 30/1.001Hz → A/B) [SMPTE260M]
Unknown Interlaced with F switching 0/1
DESCRIPTION
DESCRIPTION
10
3.4 FLY WHEEL OPERATION
The flywheel logic checks the incoming video data for valid
video lines. If the incoming data represents a valid line, the
flywheel remains in sync with the incoming data. If the
incoming data represents an invalid line, the flywheel uses
the stored timing information for the past valid line to
generate the output HVF timing signals. When three
consecutive lines having identical timing are detected, this
new timing information is saved and the flywheel operation
is updated to this new timing. Mismatches between the HVF
information decoded from the data stream and that
indicated by the flywheel will trigger the EAV_ERR and
SAV_ERR signals as shown in Figure 3. HVF output timing is
shown in Figure 2.
3.5 AUTOMATIC SWITCH LINE LOCK HANDLING
The automatic switch line lock is based on the assumption
that switching occurs between video sources of the same
format. In other words, the switching of video sources
causes only the H signal to be out of alignment whereas V
and F signals remain in sync. Therefore, when in the
automatic switch line lock mode (FAST_LOCK transitions for
low to high), the flywheel positive H signal transition aligns
with the detected positive H signal transition. Timing for the
FAST_LOCK signal is shown in Figure 5.
3.6 FIFO
The device does not flag transmission errors which might
exist in the ANC data packages. The internal FIFO is 1024
words deep for each of LUMA and CHROMA channels. For
those formats where the HANC region is greater than 1024
words, the user must take steps to ensure the FIFO does
not overflow, otherwise data may be lost. The GS1500
provides status signals to indicate the current content level
of the internal FIFO buffers, as described in section 6.1.
3.6.1 FIFO Status Bits
The device provides status output signals FF_STA[2:0] that
indicate the state of the current content level of the internal
FIFO buffers. If the extracted ANC data have completely
filled the internal FIFO buffer, FF_STA[2:0] outputs 110.
When the internal FIFO is full, any attempt to write data into
the FIFO will cause the FIFO to overrun. The device flags
this overrun state by setting FF_STA[2:0]=111 and no more
data will be extracted from the video stream.
If all ANC data in the FIFO is accessed by the user through
the FIFO interface and the internal FIFO becomes empty,
then FF_STA[2:0] outputs 001. When the internal FIFO is
empty, any attempt to read data from the FIFO will cause
the FIFO to under run. The device flags this under run state
by setting FF_STA[2:0]=000.
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