SAA5531 Philips Semiconductors, SAA5531 Datasheet - Page 67

• Manufacturer Part Number: SAA5531
• Description: Enhanced TV microcontrollers with On-Screen Display OSD
• Manufacturer: Philips Semiconductors

Philips Semiconductors
19.5
A number of attributes are available that affect the whole
display region, and cannot be applied selectively to
regions of the display.
19.5.1
The number of TV scan lines per field used for each
display row can be defined, the value is independent of the
character size being used. The number of lines can be
either 10, 13 or 16 per display row. The number of TV scan
lines per row is defined TXT21.DISP LINES<1:0>.
A value of 9 lines per row can be achieved if the display is
forced into 525-line display mode by
TXT17.FORCE DISP<1:0>, or if the device is in 10 line
mode and the automatic detection circuitry within display
finds 525-line display syncs.
19.5.2
There are three different character matrices available,
these are 12
made using TXT21.CHAR SIZE<1:0> and is independent
of the number of display lines per row.
If the character matrix is less than the number of TV scan
lines per row then the matrix is padded with blank lines.
If the character matrix is greater than the number of
TV scan lines then the character is truncated.
Table 23 Selection of Display modes
Table 24 TXT display control bits
2000 Feb 23
MOD1
Enhanced TV microcontrollers with
On-Screen Display (OSD)
PICTURE ON
0
0
1
1
Screen and global controls
TV
C
0
0
0
1
1
1
HARACTER MATRIX
MOD0
SCAN LINES PER ROW
0
1
0
1
10, 12
Video
Full Text
Mixed Screen Colour Displays screen colour at all locations not covered by character foreground,
Mixed Video
DISPLAY MODE
13 and 12
TEXT ON
(H
0
1
1
0
1
1
V)
16. The selection is
Disables all display activities, sets the RGB to true black and VDS to video.
Displays screen colour at all locations not covered by character foreground
or background colour. The box attribute has no effect.
within boxed areas or, background colour.
Displays video at all locations not covered by character foreground, within
boxed areas or, background colour.
BACKGROUND ON
X
X
0
1
0
1
67
19.5.3
CC: When attributes superimpose or boxing (see
Table 22, Serial Mode 0/1, bit 6) are set, the resulting
display depends on the setting of the following screen
control mode bits in the MMR Display Control.
TXT: The display mode is controlled by the bits in the
TXT5 and TXT6. There are 3 control functions - Text on,
Background on and Picture on. Separate sets of bits are
used inside and outside teletext boxes so that different
display modes can be invoked. TXT6 is used if the
newsflash (C5) or subtitle (C6) bits in row 25 of the basic
page memory are set otherwise TXT5 is used. This allows
the software to set up the type of display required on
newsflash and subtitle pages (e.g. text inside boxes,
TV picture outside) this will be invoked without any further
software intervention when such a page is acquired.
When teletext box control characters are present in the
display page memory, the appropriate Box control bit must
be set, TXT7.BOX ON 0, TXT7.BOX ON 1
TXT7.BOX ON 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. 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.
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
D
ISPLAY MODES
DESCRIPTION
EFFECT
Preliminary specification
SAA55xx
23 or