SAA5290ZP Philips Semiconductors, SAA5290ZP Datasheet - Page 24

• Manufacturer Part Number: SAA5290ZP
• Description: One page Economy Teletext/TV microcontroller
• Manufacturer: Philips Semiconductors

Philips Semiconductors
Teletext acquisition
The SAA5290 is able to acquire 625-line World System
Teletext. Teletext is acquired under control of the on-board
80C51 microcontroller. Pages are requested by writing a
series of bytes into the TXT3 SFR which corresponds to
the number of the page required. The bytes written into
TXT3 are put into a small RAM with an auto-incrementing
address. The start address for the RAM is set using the
SFR TXT2 register. Table 13 shows the contents of the
page request RAM.
Table 13 Register map for page requests (TXT3); note 1
Note
1. X = don't care.
Page memory organization
The acquired teletext packets each contain 40 bytes of
data and one packet is stored in each row of the text
memory. The page memory organization is given in Fig.5.
Rows 0 to 23 form the teletext page; Row 24 is available
for status messages and FLOF/FASTEXT prompt
information.
February 1995
One page Economy Teletext/TV
microcontroller
COLUMN
START
0
1
2
3
4
5
6
DO CARE
Magazine
DO CARE
Page tens
DO CARE
Page units
DO CARE
Hours tens
DO CARE
Hours units
DO CARE
Minutes tens
DO CARE
Minutes units
PRD4
HOLD
PT3
PU3
X
HU3
X
MU3
PRD3
24
MAG2
PT2
PU2
X
HU2
MT2
MU2
If the ‘DO CARE’ bit for part of the page number is set to
logic 0 then that part of the page number is ignored when
the acquisition section is deciding whether a page being
received off air should be stored or not. For example if the
‘DO CARE’ bits for the 4 subcode digits are all set to
logic 0 then every subcode version of the page will be
captured.
When the ‘HOLD' bit is set to logic 0 the acquisition section
will not recognize any page as having the correct page
number and no pages will be captured.
PRD2
MAG1
PT1
PU1
HT1
HU1
MT1
MU1
PRD1
Preliminary specification
MAG0
PT0
PU0
HT0
HU0
MT0
MU0
SAA5290
PRD0