
Arch
23 Wed May 28 17:36:23 1997
Draft 1/21/97
L64007 MPEG-2, DVB, JSAT Transport Demultiplexer Technical Manual
2-23
PRE.4 for Rev. D
Copyright 1997 by LSI Logic Corporation. All rights reserved.
The numbers in the gure indicate the byte count from the start of a sec-
tion. Bytes that are ltered are shown hatched (i.e., byte 1 and bytes 4
through 14). Bytes 2 and 3 are not ltered.
For each byte in the section that is ltered, there are two bytes that con-
stitute the lter pattern: a match byte, and a mask byte. The match byte
is the bit pattern that is compared against the section byte to determine
if there is a match. The mask byte is used to create a “don’t care” con-
dition. Although lter data is processed in bytes, the lter is a bitwise l-
ter. The following truth table shows the lter operation for each bit of
section, match, and mask data.
Each section is compared against 32 different 12-byte match/mask pat-
terns. A section can be compared against all 32 patterns.
A 32-bit lter-enable word provides control over which of the 32 different
lters are applied to a section. There is one such control word for each
group 0 PID index. Each bit of the control word corresponds to a lter
pattern. When that bit is 1, the lter is active; when it is 0, the lter is
Figure 2.20 shows a ow chart of the section ltering procedure, which
is implemented in the L64007 section ltering logic.
data
match
mask
lter result
00
0
01
0
11
0
10
0
XX
1
match
no match
match