saa5288 NXP Semiconductors, saa5288 Datasheet - Page 26

• Manufacturer Part Number: saa5288
• Description: Microcontroller With Full Screen Screen Display
• Manufacturer: NXP Semiconductors

Philips Semiconductors
7.7
The size implying OSD control characters (BCH to BFH)
are intended to allow OSD messages to be displayed.
OSD boxes are not the same as teletext boxes created
using the teletext boxing control characters
(0AH and 0BH).
When one of these characters occurs the display size
changes appropriately (to normal size for BCH, double
height for BDH, double width for BEH and double size for
BFH) and an OSD box starts from the next character
position (‘set after’). The OSD box ends either at the end
of the row of text or at the next size implying OSD
character. When an OSD box is ended using another size
implying OSD character the box ends at the position of the
control character (‘set at’). This arrangement allows
displays to be created without blank spaces at the ends of
the OSD boxes.
To prevent teletext control characters from affecting the
display of the OSD message the flash, teletext box,
conceal, separated graphics, twist and hold graphics
functions are all reset at the start of an OSD box, as they
are at the start of the row. In order to allow the most
commonly used display attributes to be set-up before the
box starts the foreground colour, background colour and
mosaics on/off attributes are not reset.
The text within an OSD box is always displayed in text
mode i.e. as if the Text On and Bkgnd On bits are both set
to a logic 1. The type of display produced inside an OSD
box is, therefore, dependant on the states of the
TXT4.SHADOW ENABLE, TXT4.TRANS ENABLE,
TXT4.BMESH ENABLE and TXT4.CMESH ENABLE
register bits, as described previously. OSD boxes can only
be displayed in TV mode i.e. when the Picture On SFR bit
is a logic 1 and the Text On SFR bit is a logic 0, both inside
and outside text boxes and for both normal and
newsflash/subtitle pages. The display of OSD boxes is not
affected by the C7, suppress header, and C10, inhibit
display, control bits stored in row 25 of the page memory.
1997 Jun 24
TV microcontroller with full screen
On Screen Display (OSD)
On Screen Display boxes
26
7.8
The register bits TXT17.SCREEN COL2-0 can be used to
define a colour to be displayed in place of the TV picture
and the black background colour. If the bits are all set to 0,
the screen colour is defined as ‘transparent’ and the TV
picture and background colour are displayed as normal.
Screen colour is displayed from 10.5 to 62.5 s 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.
When the screen colour has been redefined, no TV picture
is displayed so the Frame de-interlace output can be
activated, if the SFR bits controlling FRAME are set up to
allow this.
Table 15 Screen colours
7.9
If the TXT7.CURSOR ON bit is set, a cursor is displayed.
The cursor operates by reversing the background and
foreground colours in the character position pointed to by
the active row and column bits in the TXT9 and TXT10
SFRs.
Setting the TXT9.CURSOR FREEZE bit, causes the
cursor to stay in its current position, no matter what
happens to the active row and column positions. This
means that the software can read data from the memory
(e.g. TOP table information) without affecting the position
of the cursor.
SCREEN
COL 2
0
0
0
0
1
1
1
1
Screen colour
Cursor
SCREEN
COL 1
0
0
1
1
0
0
1
1
SCREEN
COL 0
Preliminary specification
0
1
0
1
0
1
0
1
SAA5288
transparent
red
green
yellow
blue
magenta
cyan
white
COLOUR
SCREEN