G2R-14-12VDC Datasheet, PDF (54/73 Pages) Texas Instruments – Ultralow Power NTSC/PAL/SECAM Video Decoder With RObust Sync Detector

2.20.53 Teletext Filter and Mask Registers
Address
Default
B1h–BAh
00h
ADDRESS
7
6
5
4
3
2
1
0
B1h
Filter 1 mask 1
Filter 1 pattern 1
B2h
Filter 1 mask 2
Filter 1 pattern 2
B3h
Filter 1 mask 3
Filter 1 pattern 3
B4h
Filter 1 mask 4
Filter 1 pattern 4
B5h
Filter 1 mask 5
Filter 1 pattern 5
B6h
Filter 2 mask 1
Filter 2 pattern 1
B7h
Filter 2 mask 2
Filter 2 pattern 2
B8h
Filter 2 mask 3
Filter 2 pattern 3
B9h
Filter 2 mask 4
Filter 2 pattern 4
BAh
Filter 2 mask 5
Filter 2 pattern 5
For an NABTS system, the packet prefix consists of five bytes. Each byte contains four data bits (D[3:0]) interlaced
with four Hamming protection bits (H[3:0]):
Bit 7
D[3]
Bit 6
H[3]
Bit 5
D[2]
Bit 4
H[2]
Bit 3
D[1]
Bit 2
H[1]
Bit 1
D[0]
Bit 0
H[0]
Only the data portion D[3:0] from each byte is applied to a teletext filter function with the corresponding pattern bits
P[3:0] and mask bits M[3:0]. Hamming protection bits are ignored by the filter.
For a WST system (PAL or NTSC), the packet prefix consists of two bytes so that two patterns are used. Patterns
3, 4, and 5 are ignored.
The mask bits enable filtering using the corresponding bit in the pattern register. For example, a 1 in the LSB of mask 1
means that the filter module must compare the LSB of nibble 1 in the pattern register to the first data bit on the
transaction. If these match, then a true result is returned. A 0 in a bit of mask 1 means that the filter module must ignore
that data bit of the transaction. If all 0s are programmed in the mask bits, then the filter matches all patterns returning
a true result (default 00h).
Pattern and mask for each byte and filter are referred as <1,2><P,M><1,2,3,4,5> where:
<1,2> identifies the filter 1 or 2
<P,M> identifies the pattern or mask
<1,2,3,4,5> identifies the byte number
2−43