TDA9554PS datasheet(40/125 Pages) PHILIPS

40 / 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

and to display each page header as it arrives until the

correct page has been found.

When a page request is changed (i.e.: when the TXT3

SFR is written to) a flag (PBLF) is written into bit 5, column

9, row 25 of the corresponding block of the page memory.

The state of the flag for each block is updated every TV

line, if it is set for the current display block, the acquisition

section writes all valid page headers which arrive into the

display block and automatically writes an alpha-numerics

green character into column 7 of row 0 of the display block

every TV line.

When a requested page header is acquired for the first

time, rows 1 to 23 of the relevant memory block are

cleared to space, i.e.: have 20h written into every column,

before the rest of the page arrives. Row 24 is also cleared

if the TXT0.X24 POSN bit is set. If the TXT1.EXT PKT OFF

bit is set the extension packets corresponding to the page

are also cleared.

The last 8 characters of the page header are used to

provide a time display and are always extracted from every

valid page header as it arrives and written into the display

block

The TXT0. DISABLE HEADER ROLL bit prevents any

data being written into row 0 of the page memory except

when a page is acquired off air i.e.: rolling headers and

time are not written into the memory. The TXT1.ACQ OFF

bit prevents any data being written into the memory by the

teletext acquisition section.

When a parallel magazine mode transmission is being

received only headers in the magazine of the page

requested are considered valid for the purposes of rolling

headers and time. Only one magazine is used even if don't

care magazine is requested. When a serial magazine

mode transmission is being received all page headers are

considered to be valid.

Error Checking

Before teletext packets are written into the page memory

they are error checked. The error checking carried out

depends on the packet number, the byte number, the error

check mode bits in the page request data and the TXT1.8

BIT bit.

If an incorrectable error occurs in one of the Hamming

checked addressing and control bytes in the page header

or in the Hamming checked bytes in packet 8/30, bit 4 of

the byte written into the memory is set, to act as an error

flag to the software. If incorrectable errors are detected in

any other Hamming checked data the byte is not written

into the memory.

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 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 14 bytes are

unused and may be used by the software, if necessary.

Row 25 Data Contents

The Hamming error flags are set if the on-board 8/4

Hamming checker detects that there has been an

incorrectable (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 incorrectable errors if

that part of the page request was a 'don't care'. There is no

error flag for the magazine number as an incorrectable

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.

The newsflash (C5), subtitle (C6), suppress header (C7),

inhibit display (C10) and language control (C12 to 14) bits

are dealt with automatically by the display section,

described below.

The update (C8) bit has no effect on the hardware. The

remaining 32 bytes of the page header are parity checked

and written into columns 8 to 39 of row 0. Bytes which pass

the parity check have the MSB set to 0 and are written into

the page memory. Bytes with parity errors are not written

into the memory.

Inventory Page

If the TXT0.INV on bit is 1, memory block 8 is used as an

inventory page. The inventory page consists of two tables,

- the Transmitted Page Table (TPT) and the subtitle page

table (SPT).

In each table, every possible combination of the page tens

and units digit, 00 to FFh, is represented by a byte. Each

bit of these bytes corresponds to a magazine number so

each page number, from 100 to 8FF, is represented by a

bit in the table.The bit for a particular page in the TPT is set

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