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TDA9351PS/N2 View Datasheet(PDF) - Philips Electronics

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TDA9351PS/N2 Datasheet PDF : 118 Pages
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Philips Semiconductors
TV signal processor-Teletext decoder with
embedded µ-Controller
Tentative Device Specification
TDA935X/6X/8X PS/N2 series
when a page header is received for that page. The bit in
the SPT is set when a page header for the page is received
which has the ‘subtitle’ page header control bit (C6)
set.The bit for a particular page in the TPT is set when a
page header is received for that page. The bit in the SPT
is set when a page header for the page is received which
has the ‘subtitle’ page header control bit (C6) set.
Packet 26 Processing
One of the uses of packet 26 is to transmit characters
which are not in the basic teletext character set. The family
automatically decodes packet 26 data and, if a character
corresponding to that being transmitted is available in the
character set, automatically writes the appropriate
character code into the correct location in the teletext
memory. This is not a full implementation of the packet 26
specification allowed for in level 2 teletext, and so is often
referred to as level 1.5.
By convention, the packets 26 for a page are transmitted
before the normal packets. To prevent the default
character data over writing the packet 26 data the device
incorporates a mechanism which prevents packet 26 data
from being overwritten. This mechanism is disabled when
the Spanish national option is detected as the Spanish
transmission system sends even parity (i.e. incorrect)
characters in the basic page locations corresponding to
the characters sent via packet 26 and these will not over
write the packet 26 characters anyway. The special
treatment of Spanish national option is prevented if
TXT12. ROM VER R4 is logic 0 or if the TXT8.DISABLE
SPANISH is set.
Packet 26 data is processed regardless of the TXT1. EXT
PKT OFF bit, but setting theTXT1.X26 OFF disables
packet 26 processing.
The TXT8. Packet 26 received bit is set by the hardware
whenever a character is written into the page memory by
the packet 26 decoding hardware. The flag can be reset by
writing a 0 into the SFR bit.
525 WST
The 525 line format is similar to the 625 line format but the
data rate is lower and there are less data bytes per packet
(32 rather than 40). There are still 40 characters per
display row so extra packets are sent each of which
contains the last 8 characters for four rows. These packets
can be identified by looking at the ‘tabulation bit’ (T), which
replaces one of the magazine bits in 525 line teletext.
When an ordinary packet with T = 1 is received, the
decoder puts the data into the four rows starting with that
corresponding to the packet number, but with the 2 LSBs
set to 0. For example, a packet 9 with T = 1 (packet X/1/9)
contains data for rows 8, 9, 10 and 11. The error checking
carried out on data from packets with T = 1 depends on the
setting of the TXT1. 8 BIT bit and the error checking control
bits in the page request data and is the same as that
applied to the data written into the same memory location
in the 625 line format.
The rolling time display (the last 8 characters in row 0) is
taken from any packets X/1/1, 2 or 3 received. In parallel
magazine mode only packets in the correct magazine are
used for rolling time. Packet number X/1/0 is ignored.
The tabulation bit is also used with extension packets. The
first 8 data bytes of packet X/1/24 are used to extend the
Fastext prompt row to 40 characters. These characters are
written into whichever part of the memory the packet 24 is
being written into (determined by the ‘X24 Posn’ bit).
Packets X/0/27/0 contain 5 Fastext page links and the link
control byte and are captured, Hamming checked and
stored by in the same way as are packets X/27/0 in 625
line text. Packets X/1/27/0 are not captured.
Because there are only 2 magazine bits in 525 line text,
packets with the magazine bits all set to 0 are referred to
as being in magazine 4. Therefore, the broadcast service
data packet is packet 4/30, rather than packet 8/30. As in
625 line text, the first 20 bytes of packet 4/30 contain
encoded data which is decoded in the same way as that in
packet 8/30. The last 12 bytes of the packet contains half
of the parity encoded status message. Packet 4/0/30
contains the first half of the message and packet 4/1/30
contains the second half. The last 4 bytes of the message
are not written into memory. The first 20 bytes of the each
version of the packet are the same so they are stored
whenever either version of the packet is acquired.
In 525 line text each packet 26 only contains ten 24/18
Hamming encoded data triplets, rather than the 13 found
in 625 line text. The tabulation bit is used as an extra bit
(the MSB) of the designation code, allowing 32 packet 26s
to be transmitted for each page. The last byte of each
packet 26 is ignored.
FASTEXT DETECTION
When a packet 27, designation code 0 is detected,
whether or not it is acquired, the TXT13. FASTEXT bit is
set. If the device is receiving 525 line teletext, a packet
X/0/27/0 is required to set the flag. The flag can be reset
by writing a 0 into the SFR bit.
BROADCAST SERVICE DATA DETECTION
When a packet 8/30 is detected, or a packet 4/30 when the
device is receiving a 525 line transmission, the TXT13.
Packet 8/30. The flag can be reset by writing a 0 into the
SFR bit.
VPS ACQUISITION
When the TXT0. VPS ON bit is set, any VPS data present
on line 16, field 0 of the CVBS signal at the input of the
2001 Jan 18
39
 

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