
Philips Semiconductors
Preliminary specification
1999 Sep 28
71
TV signal processor-Teletext decoder with
embedded
μ
-Controller
TDA 935X/6X/8X series
.
When Teletext box control characters are present in the display page memory, the appropriate Box control bit
must be set, TXT7.Boxes On Row 0, TXT7.Boxes On Row 1 - 23 or TXT7.Boxes On Row 24. This allows the
display mode to be different inside the Teletext box compared to outside. These bits are present to allow boxes
in certain areas of the screen to be disabled. So that Teletext boxes can be used for the display of OSD
messages without the danger of subtitles in boxes, which may also be in the display page memory, being
displayed. The use of teletext boxes for OSD messages has been superseded in this device by the OSD box
concept, but these bits remain to allow teletext boxes to be used, if required.
S
CREEN
C
OLOUR
CC:- The screen colour is defined by REG0:Display Control and points to a location in the CLUT table. The
screen colour covers the full video width. It is visible when the Full Text or Mixed Screen Colour mode is set and
no foreground or background pixels are being displayed.
TXT:- The register bits TXT17.SCREEN COL<2:0> can be used to define a colour to be displayed in place of
TV picture and the black background colour. If the bits are all set to 0, the screen colour is defined as
‘transparent’ and TV picture and background colour are displayed as normal. Otherwise the bits define CLUT
entries 9 to 15.
Screen colour is displayed from 10.5 ms to 62.5 ms after the active edge of the HSync input and on TV lines 23
to 310 inclusive, for a 625 line display, and lines 17 to 260 inclusive for a 525 line display.
Text Display Controls
T
EXT
D
ISPLAY
C
ONFIGURATION
(CC
MODE
)
Two types of areas are possible. The one area is static and the other is dynamic. The dynamic area allows
scrolling of a region to take place. The areas cannot cross each other. Only one scroll region is possible.
Display Map
The display map allows a flexible allocation of data in the memory to individual rows.
Sixteen words are provided in the display memory for this purpose. The lower 10 bits address the first word in
the memory where the row data starts. The most significant bit enables the display when not within the scroll
(dynamic) area.
The display map memory is fixed at the first 16 words in the closed caption display memory.
Picture On
Text On
Background On
Effect
0
0
0
1
1
1
0
1
1
0
1
1
x
0
1
x
0
1
Text mode, black screen
Text mode, background always black
Text mode
Video mode
Mixed text and TV mode
Text mode, TV picture outside text area
Table 23 TXT Display Control Bits