SAA5531 Philips Semiconductors, SAA5531 Datasheet - Page 49

• Manufacturer Part Number: SAA5531
• Description: Enhanced TV microcontrollers with On-Screen Display OSD
• Manufacturer: Philips Semiconductors

Philips Semiconductors
18.1.6.4
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.
2000 Feb 23
handbook, full pagewidth
Enhanced TV microcontrollers with
On-Screen Display (OSD)
(1) If ‘X24 POSN’ bit = 0.
(2) Byte 10 reserved.
Teletext memory organisation
Row
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
0
1
2
3
4
5
6
7
8
9
0
Extension Packet Block (9)
Fig.19 Extension packet storage locations.
9
10
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
(2)
VPS Data
49
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.
23
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(1)
GSA002
Preliminary specification
SAA55xx