參數(shù)資料
型號: TDA936X
廠商: NXP Semiconductors N.V.
英文描述: TV signal processor-Teletext decoder with embedded m-Controller
中文描述: 電視信號處理器與嵌入式米圖文電視解碼器控制器
文件頁數(shù): 48/140頁
文件大小: 570K
代理商: TDA936X
Philips Semiconductors
Preliminary specification
1999 Sep 28
48
TV signal processor-Teletext decoder with
embedded
μ
-Controller
TDA 935X/6X/8X series
M
AKING A
P
AGE
R
EQUEST
A page is requested by writing a series of bytes into the TXT3.PRD<4:0> SFR which corresponds 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 13 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.
If the ‘Do Care’ bit for part of the page number is set logic 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 four 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 a logic 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.
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.
.
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
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 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
Start
Column
Byte
Identification
PRD<4>
PRD<3>
PRD<2>
PRD<1>
PRD<0>
0
1
2
3
4
5
6
7
Magazine
Page Tens
Page Units
Hours Tens
Hours Units
Minutes Tens
Minutes Units
Error Mode
DO CARE
DO CARE
DO CARE
DO CARE
DO CARE
DO CARE
DO CARE
x
HOLD
PT3
PU3
x
HU3
x
MU3
x
MAG2
PT2
PU2
x
HU2
MT2
MU2
x
MAG1
PT1
PU1
HT1
HU1
MT1
MU1
E1
MAG0
PT0
PU0
HT0
HU0
MT0
MU0
E0
Table 13 The contents of the Page Request RAM
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