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2–56
2.15.28 TXF Filter #1 Parameters
VIP address
190 – 194
VMI address
90 – 94
I2C address
90 – 94
Address
7
6
5
4
3
2
1
0
90
Filter #1 mask_1[3:0]
Filter #1 pattern_1[3:0]
91
Filter #1 mask_2[3:0]
Filter #1 pattern_2[3:0]
92
Filter #1 mask_3[3:0]
Filter #1 pattern_3[3:0]
93
Filter #1 mask_4[3:0]
Filter #1 pattern_4[3:0]
94
Filter #1 mask_5[3:0]
Filter #1 pattern_5[3:0]
These registers hold the search parameters for filter #1. The parameters parse the first five bytes of NABTS
teletext transactions or the first two bytes of WST transactions. These bytes of teletext always contain four
data bits interlaced with four hamming protection bits. The filter ignores the protection bits.
For an NABTS system, the packet prefix consists of five bytes: P1, P2, P3, CI, and PS. Each byte contains
4 data bits interlaced with 4 hamming protection bits.
Pattern_1[3:0] corresponds to P1[7], P1[5], P1[3], P1[1]
(Packet address)
Pattern_2[3:0] corresponds to P2[7], P2[5], P2[3], P2[1]
(Packet address)
Pattern_3[3:0] corresponds to P3[7], P3[5], P3[3], P3[1]
(Packet address)
Pattern_4[3:0] corresponds to CI[7], CI[5], CI[3], CI[1]
(Continuity index)
Pattern_5[3:0] corresponds to PS[7], PS[5], PS[3], PS[1]
(Packet structure)
For a WST system (PAL or NTSC), the magazine and row address group consists of two bytes. The two
bytes contain three bits of magazine number (M[2:0]) and 5 bits of row address (R[4:0]), interlaced with eight
hamming protection bits.
Pattern_1[3:0] corresponds to R[0], M[2], M[1], M[0]
(Magazine and row LSBit)
Pattern_2[3:0] corresponds to R[4], R[3], R2], R[1]
(Upper bits of row address)
Pattern_3[3:0] is ignored
Pattern_4[3:0] is ignored
Pattern_5[3:0] is 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 VBI data processor (VDP) should compare the LSB of Nybble_1 in the pattern
register to the first data bit of the transaction. A 0 in the LSB of Mask_1 means that the VDP should ignore
the first data bit of the transaction.
NOTE:
The TXF filter #1 parameters can only be written and read when both the filter #1
enable and the filter #2 enable bits are 0. When reading the values, the values must
be read consecutively, starting with the first value.