TDA9554PS datasheet(39/125 Pages) PHILIPS

39 / 125 page

2000 Jun 22

Philips Semiconductors

Tentative Device Speciﬁcation

TV signal processor-Teletext decoder with

embedded

µ-Controller

TDA955X/6X/8X PS/N1 series

Data Standards

The data and clock standards that can be recovered are

shown in Table 10 below:-

Data Capture Timing

The Data Capture timing section uses the Synchronisation

information extracted from the CVBS signal to generate

the required Horizontal and Vertical reference timings.

The timing section automatically recognises and selects

the appropriate timings for either 625 (50Hz)

synchronisation or 525 (60Hz) synchronisation. A flag

TXT12.Video Signal Quality is set when the timing section

is locked correctly to the incoming CVBS signal. When

TXT12.Video Signal Quality is set another flag

TXT12.625/525 SYNC can be used to identify the

standard.

Acquisition

The acquisition sections extracts the relevant information

from the serial stream of data from the MulVIP and stores

it in memory.

625 WST ACQUISITION

The family is capable of acquiring 625-line and 525-line

World System Teletext. Teletext pages are identified by

seven numbers: magazine (page hundreds), page tens,

page units, hours tens, hours units, minutes tens and

minutes units. The last four digits, hours and minutes, are

known as the subcode, and were originally intended to be

time related, hence their names.

Making a page request

A page is requested by writing a series of bytes into the

TXT3.PRD<4:0> SFR which correspond to the number of

the page required. The bytes written into TXT3 are stored

in a RAM with an auto-incrementing address. The start

address for the RAM is set using the TXT2.SC<2:0> to

define which part of the page request is being written, and

TXT2.REQ<3:0> is used to define which of the 10 page

requests is being modified. If TXT2.REQ<3:0> is greater

than 09h, then data being written to TXT3 is ignored. Table

11 shows the contents of the page request RAM.

Up to 10 pages of teletext can be acquired on the 10 page

device, when TXT1.EXT PKT OFF is set to logic 1, and up

to 9 pages can be acquired when this bit is set to logic 0.

f the 'Do Care' bit for part of the page number is set to 0

then that part of the page number is ignored when the

teletext decoder 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 0 then

every subcode version of the page will be captured.

Table 11 The contents of the Page request RAM

Note: MAG = Magazine PT = Page Tens PU = Page Units

HT = Hours Tens HU = Hours Units

MT = Minutes Tens MU = Minutes Units E = Error check

mode

When the Hold bit is set to 0 the teletext decoder will not

recognise any page as having the correct page number

and no pages will be captured. In addition to providing the

user requested hold function this bit should be used to

prevent the inadvertent capture of an unwanted page

when a new page request is being made. For example, if

the previous page request was for page 100 and this was

being changed to page 234, it would be possible to capture

page 200 if this arrived after only the requested magazine

number had been changed.

The E1 and E0 bits control the error checking which should

be carried out on packets 1 to 23 when the page being

requested is captured. This is described in more detail in a

later section (‘Error Checking’).

For a multi page device, each packet can only be written

into one place in the teletext RAM so if a page matches

more than one of the page requests the data is written into

the area of memory corresponding to the lowest numbered

matching page request.

At power-up each page request defaults to any page, hold

on and error check mode 0.

Rolling Headers and Time

When a new page has been requested it is conventional

for the decoder to turn the header row of the display green

Data Standard

Clock Rate

625WST

6.9375 MHz

525WST

5.7272 MHz

VPS

5.0 MHz

WSS

5.0 MHz

Closed Caption

500 KHz

Table 10 Data Slicing Standards

Start

Column

Byte

Identiﬁcation

PRD<4>

PRD<3>

PRD<2>

PRD<1>

PRD<0>

Magazine

DO CARE

HOLD

MAG2

MAG1

MAG0

Page Tens

DO CARE

PT3

PT2

PT1

PT0

Page Units

DO CARE

PU3

PU2

PU1

PU0

Hours Tens

DO CARE

HT1

HT0

Hours Units

DO CARE

HU3

HU2

HU1

HU0

Minutes Tens

DO CARE

MT2

MT1

MT0

Minutes Units

DO CARE

MU3

MU2

MU1

MU0

Error Mode

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