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Full-Field Mode
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8 Full-Field Mode
Some teletext services transmit data on multiple video lines occurring anywhere in the video field. The
TVP5154A provides a full-field mode which arms VDP slicing for all lines in the video field. When full-field
mode is enabled, all video lines excluding those defined in the line-mode registers are sliced as specified
in the VDP full-field mode register (FCh). The full-field mode register uses the same mode configuration
format as the line-mode registers. Full-field mode is enabled by setting the full-field enable bit in register
CFh to a logic 1. Sliced data is then retrieved by I
2
C FIFO access or as ancillary data in the ITU-R BT.656
data stream.
9 VBI Raw Data Mode
The TVP5154A offers a VBI raw data mode for use in systems where VBI data slicing and processing is
handled in the digital backend receiver instead of the video decoder. In this mode of operation, the
decoders are configured to output raw 2x over-sampled luma data on the ITU-R BT.656 output during the
defined VBLK (vertical blanking) interval. The raw, un-sliced A/D video data is transmitted during the
active video portion of the line with chroma samples being replaced with the luma samples.
The default VBLK interval for Field 1 is defined as lines 1 through 20 for 525-line video formats and lines
623 through 23 for 625-line video formats. This interval may be adjusted to include additional lines.
Support for NTSC line 21 closed caption data, for example, requires extension of the VBLK interval to
include line 21.
The default VBLK interval for the TVP5154A is defined as lines 1 through 20 for 525-line video formats
and lines 623 through 23 for 625-line formats. The TVP5154A VBLK interval can be adjusted with the
VBLK Start and Stop registers (18h-19h). The TVP5154A VBLK Start and Stop registers provide relative
adjustments to the default VBLK interval. After configuring the desire VBLK interval, the Luma bypass (bit
4) in the Luminance Processing Control #1 register (07h) must be set to a logic 1 to enable raw data
output.
Table 6 shows the default I
2
C registers with a modified VBLK interval for Line 21 inclusion, while
Table 7 shows the default 625-line setup. Also shown in Figure 5 and Figure 6 are digital captures of the
TVP5154A ITU-R BT.656 output for comparison of normal operation and raw data operation. Insertion of a
4-byte preamble (00h FFh FFh 60h) prior to the start of the raw data is optional in I
2
C register 07h.
Table 6. 525-Line Raw Data Setup to Include Line 21
I
2
C Subaddress Default I
2
C Data Description
07h 00h 10h Enable raw data (Luma bypass) and Preamble
18h 00h 00h VBLK Start = default line 1
19h 00h 01h VBLK Stop = d1 to include line 21
Table 7. 625-Line Raw Data Setup
I
2
C Subaddress Default I
2
C Data Description
07h 00h 10h Enable raw data (Luma bypass) and Preamble
18h 00h 00h VBLK Start = default line 623
19h 00h 00h VBLK Stop = default
Note: Detailed descriptions of the TVP5154A I
2
C registers related to VBI Raw Data Mode are shown in
Appendix A.
Example (set up NTSC for raw data on lines 1 through 21)
1. Set up VBLK interval.
• Write 01h to register 19h to include line 21.
2. Enable Raw Data Mode
• Write 10h to register 07h to enable raw data mode.
10 TVP5154A VBI Quick Start SLEA104 – July 2010
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