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Functional Description
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SLES140A—March 2007 TVP5147M1PFP
2.11.66 VDP TTX Filter And Mask Registers
Subaddress B1h B2h B3h B4h B5h B6h B7h B8h B9h BAh
Default 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h
Subaddress 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 4 data bits (D[3:0])
interlaced with 4 Hamming protection bits (H[3:0]):
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
D[3] H[3] D[2] H[2] D[1] H[1] D[0] H[0]
Only data portion D[3:0] from each byte is applied to a teletext filter function with corresponding pattern bits
P[3:0] and mask bits M[3:0]. The filter ignores the Hamming protection bits.
For WST system (PAL or NTSC), the packet prefix consists of two bytes. The two bytes contain three bits of
magazine number (M[2:0]) and five bits of row address (R[4:0]), interlaced with eight Hamming protection bits
H[7:0]:
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
R[0] H[3] M[2] H[2] M[1] H[1] M[0] H[0]
R[4] H[7] R[3] H[6] R[2] H[5] R[1] H[4]
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 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).