hmp8117 Intersil Corporation, hmp8117 Datasheet - Page 18

• Manufacturer Part Number: hmp8117
• Description: Ntsc/pal Video Decoder
• Manufacturer: Intersil Corporation

NOTES:
Teletext
The HMP8117 supports ITU-R BT.653 625-line and 525-line
teletext system B, C and D capture. NABTS (North American
Broadcast Teletext Specification) is the same as BT.653
525-line system C, which is also used to transmit Intel
Intercast™ information. WST (World System Teletext) is the
same as BT.653 system B. Figure 16 shows the basic
structure of a video signal that contains teletext data.
The scan lines containing teletext information are monitored.
If teletext is enabled and teletext data is present, the teletext
data is output as BT.656 ancillary data.
DETECTION OF TELETEXT
The teletext decoder monitors the scan lines, looking for the
16-bit clock run-in (sometimes referred to as the clock
synchronization code) used by teletext. If found, it locks to
the clock run-in, the teletext data is sampled and loaded into
shift registers, and the data is then transferred to internal
holding registers.
If the clock run-in is not found, it is assumed the scan line
contains video data unless other VBI information is detected,
such as WSS.
If a teletext clock run-in is found before line 23 or line 289 for
NTSC and (M) PAL, or line 336 for (B, D, G, H, I, N, N
the VBI Teletext Detect status bit is immediately set to “1”. If not
found by these lines, the status bit is immediately reset to “0”.
28. ep = even parity for P8-P13.
29. WSS CRC data = “00 0000” during PAL operation.
30. CRC = Sum of P8-P14 of Data ID through last user data word. Preset to all zeros, carry is ignored.
Data Block Number
Data Word Count
PIXEL OUTPUT
WSS Data
WSS CRC
Preamble
Data ID
Data
CRC
TABLE 7. OUTPUTTING THE SLICED WSS DATA AS BT.656 ANCILLARY DATA
18
P15
P14
P14
P14
P14
P14
P14
P14
P14
P14
P14
P14
P14
0
1
1
bit 6
P14
ep
ep
ep
ep
ep
ep
ep
ep
ep
ep
ep
0
1
1
C
) PAL,
P13
bit 5
0
1
1
1
0
0
0
0
0
0
0
0
0
0
HMP8117
bit 4
P12
0
1
1
1
0
0
0
0
0
0
0
0
0
0
ACCESSING THE TELETEXT DATA
The teletext data must be output as BT.656 ancillary data.
The I
teletext information when needed.
Table 8 illustrates the teletext BT.656 ancillary data format
and Figure 15 depicts the portion of the incoming teletext
signal which is sliced and output as part of the ancillary data
stream. The teletext data is present during the horizontal
blanking interval after the line containing the teletext
information. The actual BT.656 bytes that contain teletext
data only contain 4 bits of the actual data packet. Note that
only the data packet of Figure 16 is sent as ancillary data;
the clock run-in is not included in the data stream.
bit 11
2
bit 7
bit 3
bit 3
bit 3
P11
C interface does not have the bandwidth to output
0
1
1
0
0
0
0
0
0
0
bit 10
bit 6
bit 2
bit 2
bit 2
P10
0
1
1
0
0
0
0
0
0
0
bit 13
bit 9
bit 5
bit 1
bit 5
bit 1
bit 1
P9
0
1
1
1
0
1
0
0
1 = even field data
0 = odd field data
bit 12
bit 8
bit 4
bit 0
bit 4
bit 0
bit 0
P8
0
1
1
1
0
0
0
April 19, 2007
FN4643.3