SAA5520 Datasheet, PDF (47/80 Pages) NXP Semiconductors – Standard TV Microcontrollers with On-Screen Display(OSD)

Philips Semiconductors
Standard TV microcontrollers with
On-Screen Display (OSD)
Preliminary specification
SAA55xx
18.1.6.4 Teletext memory organisation
The teletext memory is divided into 2 banks of 10 blocks.
Normally, when the TXT1.EXT PKT OFF bit is logic 0,
each of blocks 0 to 8 contains 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 two 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 PLBF flag but the last 14 bytes are
unused and may be used by the software, if necessary.
handbook, full pagewidth
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⁽¹⁾
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⁽¹⁾
Packet X/27/0 for page in block 1
Packet X/24 for page in block 2⁽¹⁾
Packet X/27/0 for page in block 2
Packet X/24 for page in block 3⁽¹⁾
Packet X/27/0 for page in block 3
Packet X/24 for page in block 4⁽¹⁾
Packet X/27/0 for page in block 4
Packet X/24 for page in block 5⁽¹⁾
Packet X/27/0 for page in block 5
Packet X/24 for page in block 6⁽¹⁾
Packet X/27/0 for page in block 6
Packet X/24 for page in block 7⁽¹⁾
Packet X/27/0 for page in block 7
Packet X/24 for page in block 8⁽¹⁾
Packet X/27/0 for page in block 8
Packet 8/30/4-15
VPS Data
9 10⁽²⁾
23
GSA002
(1) If ‘X24 POSN’ bit = 0.
(2) Byte 10 reserved.
Fig.18 Extension packet storage locations.
1999 Oct 27
47