
Philips Semiconductors
Preliminary specification
1999 Sep 28
52
TV signal processor-Teletext decoder with
embedded
μ
-Controller
TDA 935X/6X/8X series
Teletext Memory Organisation
The teletext memory is divided in to 10 blocks. Normally, when the TXT1.EXT PKT OFF bit is logic 0, each of
blocks 0 to 8 contain a teletext page arranged in the same way as the basic page memory of the page device
and block 9 contains extension packets. When the TXT1.EXT PKT OFF bit is logic 1, no extension packets are
captured and block 9 of the memory is used to store another page. The number of the memory block into which
a page is written corresponds to the page request number which resulted in the capture of the page.
Packet 0, the page header, is split into 2 parts when it is written into the text memory. The first 8 bytes of the
header contain control and addressing information. They are Hamming decoded and written into columns 0 to
7 of row 25. Row 25 also contains the magazine number of the acquired page and the PBLF flag but the last 13
bytes are unused and may be used by the software. Row 25, column 10 is reserved and should not be used by
software.
.
Figure 21 Teletext Extension Packet Storage Locations
R
OW
25 D
ATA
C
ONTENTS
The Hamming error flags are set if the on-board 8/4 Hamming checker detects that there has been an
uncorrectable (2 bit) error in the associated byte. It is possible for the page to still be acquired if some of the
page address information contains uncorrectable errors if that part of the page request was a 'don't care'. There
is no error flag for the magazine number as an uncorrectable error in this information prevents the page being
acquired.
The interrupted sequence (C9) bit is automatically dealt with by the acquisition section so that rolling headers
do not contain a discontinuity in the page number sequence.
The magazine serial (C11) bit indicates whether the transmission is a serial or a parallel magazine transmission.
This affects the way the acquisition section operates and is dealt with automatically.
Extension Packet Block (9)
Row 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
0
Packet X/24 for page in block 0 *
Packet X/27/0 for page in block 0
Packet 8/30/0,1
Packet 8/30/2,3
Packet X/24 for page in block 1 *
Packet X/27/0 for page in block 1
Packet X/24 for page in block 2 *
Packet X/27/0 for page in block 2
Packet X/24 for page in block 3 *
Packet X/27/0 for page in block 3
Packet X/24 for page in block 4 *
Packet X/27/0 for page in block 4
Packet X/24 for page in block 5 *
Packet X/27/0 for page in block 5
Packet X/24 for page in block 6 *
Packet X/27/0 for page in block 6
Packet X/24 for page in block 7 *
Packet X/27/0 for page in block 7
Packet X/24 for page in block 8 *
Packet X/27/0 for page in block 8
Packet 8/30/4-15
* if ‘X24 Posn’ bit = 0
NOTE:
9
23
VPS Data