Toshiba 43VR9UM Service Manual page 30

7. SUBDATA DESCRIPTION
Sub data (Design data) of Teletext circuit is as follow. Their sub data is displayed only at Design mode.
7-1 TEXT Screen Position
To adjust TEXT screen by using following subdata
- TXTH = Horizontal Position Offset for Teletext screen (1/4 Character/Step)
- TXTV = Vertical Position Offset for Teletext screen (1 line/Step)
7-2 H/V Synchronization
Teletext screen jitter occurs at the point where the Horizontal pulse to Vertical pulse timing = 1/2H. So it is recommended to
set the active edge of the Horizontal and Vertical synchronization signals to the leading edge of the pulse. A typical Horizon-
tal sync pulse will be 1/4H in duration and a typical Vertical sync pulse 500-900 _s in duration.
To adjust Horizontal and Vertical timing by using following subdata.
- TXTS(Bit3-0) = Vertical Sync Delay (0.66 _sec/step) = 0 to 41.58 _sec
To adjust the polarity of Horizontal and Vertical by using following subdata
- TXTS(Bit7) = 0: Negative Horizontal pulse at Pin 5 of UNIT
= 1: Positive Horizontal pulse at Pin 5 of UNIT
- TXTS(Bit6) = 0: Negative Vertical pulse at Pin 4 of UNIT
= 1: Positive Vertical pulse at Pin 4 of UNIT
7-3 TEXT Screen Brightness
To adjust RGB Output level of QT01 (Pin 46, 47 and 48) by using following subdata
- TXTG(Bit3-0) = RGB Output Level = 0.7V(00h) to 1.0V(0Fh)
7-4 TEXT CVBS Selection
To select CVBS through or pass the Group Delay Compensation Filter by using following subdata
It is possible to select it at each channel position (0-99 Pos), according to signal condition of each position. This solution will
be very useful for Asia market.
- SYS(Bit1) = 0: CVBS0 / Pin31 of QT01 (Using the filter)
= 1: CVBS1 / Pin32 of QT01 (Pass the filter)(Factory default setting)
8. TECHNICAL DESCRIPTION
8-1 TELETEXT
Teletext is defined in ETS 300 706 by ETSI (European Telecommunication Standard Institute).
8-1-1 TELETEXT LEVEL
Teletext data is organised to provide a range of presentation and application features. Their features have been arranged to
be downward compatible to permit initial services to be defined and existing services to be upgraded without rending
present decoders in the filed obsolete.
Presently three levels are defined:
LEVEL 1
- Alpha mosaic characters
- Spacing attributes
- Fixed colour palette
- 25 rows of 40 columns
LEVEL 1.5
Level 1.5 Display Image is shown in Fig. 8-1-1.
- Extends the character set repertoire of Level 1 with the use of X26.
Fig. 8-1-1 Level 1/1.5 Screen Image
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