saa5290ps NXP Semiconductors, saa5290ps Datasheet - Page 45

• Manufacturer Part Number: saa5290ps
• Description: Economy Teletext And Tv Microcontrollers
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9.13
The size implying OSD control characters (BCH to BFH)
are intended to allow OSD messages to be displayed with
the minimum disruption to the teletext page stored in the
page memory. 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 control characters from the teletext page
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, dependent 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.
9.14
The register bits TXT17.SCREEN COL2 to COL0 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 logic 0s, the screen colour is defined as ‘transparent’
and the TV picture and background colour are displayed
as normal.
1998 Dec 14
Economy teletext and TV microcontrollers
On-Screen Display boxes
Screen colour
45
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 21 Screen colours
9.15
The CLUT SFR can be used to load a colour look-up table
(CLUT) which allows the 8 foreground colours and
8 background colours to be redefined. Each entry has
6 bits, 2 for each colour component, giving a total palette
of 64 colours from which to choose.
When the CLUT.CLUT ENABLE bit is a logic 0 the CLUT
is disabled and the device will display the normal, full
intensity, teletext colours.
The meaning of the least significant 6 bits of the CLUT
SFR depends on the setting of the CLUT.CLUT
ADDRESS bit when the register is written to. If the
CLUT.CLUT ADDRESS bit is a logic 1, the 4 LSBs of the
SFR contain the address of the entry in the CLUT which
will be modified by subsequent writes to the CLUT SFR. If
the CLUT.CLUT ADDRESS bit is a logic 0, the 6 LSBs of
the SFR define a colour which will be written into the CLUT
at the address defined by a previous write to the CLUT
SFR. An entry is written into the CLUT whenever the CLUT
SFR is written to, unless the CLUT.CLUT ADDRESS bit is
set.
Table 22 shows which CLUT entry corresponds to which
full intensity colour. The contents of the CLUT are not reset
at power-up and should be defined by the software before
the CLUT is enabled.
SCREEN
COL 2
0
0
0
0
1
1
1
1
Redefinable colours (SAA549x)
SCREEN
COL 1
0
0
1
1
0
0
1
1
SAA5x9x family
SCREEN
COL 0
Preliminary specification
0
1
0
1
0
1
0
1
transparent
COLOUR
SCREEN
magenta
yellow
green
white
cyan
blue
red