SAA6721E Datasheet, PDF (57/72 Pages) NXP Semiconductors – SXGA RGB to TFT graphics engine

Philips Semiconductors
SXGA RGB to TFT graphics engine
Preliminary specification
SAA6721E
Table 18 OSD window size
OSD SIZE
32 × 16
40 × 20
48 × 24
OSD WINDOW
RESOLUTION/PIXELS
24 × 24
768 × 384
960 × 480
1152 × 576
12 × 16
384 × 256
480 × 320
576 × 384
The whole OSD window can be zoomed in both directions
by a factor of two by setting zoom2 to logic 1. This results
in pixel doubling horizontally and vertically.
Each character can be displayed using 1 of 8 different
foreground and background colours. These sixteen
colours can be chosen from the full true colour palette with
8 bits per colour component. The definition of these
colours is in registers 144 to 191 (see OSD section of the
programming register Table 7). The first 8 colour entries
are used for foreground colours, and the second half is
used for defining the background colours. Registers
192 to 195 (see Table 7) decide the transparency and
alpha blending effects. If one of these effects is enabled for
a specific character, only the colours defined as
transparency or alpha blending colours will be used to
generate these effects.
Each character information in the OSD window memory
consists of 15 bits of information. This is given in
Tables 19 and 20.
Table 19 Character appearance definition
CHARACTER INFORMATION
Character code
Appearance
Background colour
Foreground colour
NUMBER OF BITS
7
2
3
3
The character code is used to address the defined
characters inside the matrix memory.
The appearance bits decide about transparency and alpha
blending, and background and foreground colour are
indices to the colour definition registers.
Table 20 Colour effects
APPEARANCE
VALUE
EFFECT
0
OSD character colours are displayed
instead of the picture colours
1
OSD character colours defined as
transparency colours will be replaced
by the picture colours
2
OSD character colours defined as
alpha blending colours will be alpha
blended 1 : 1 with the picture colours
3
OSD character colours defined as
alpha blending colours will be alpha
blended 2 : 1 with the picture colours
To access a certain character position its coordinates must
be programmed into registers 196 (cursor_row) and 197
(cursor_column), see Table 7. After that, the colours and
appearance of the character must be defined in
address 198 (see Table 7). This definition is valid for all
further writes to register 199 (char_code), see Table 7.
After writing to this register the cursor position changes to
the next right position. At line end it wraps around to the
first left character in the line below. I²C-bus auto-increment
is not active at register 199 (see Table 7), so that
subsequent I²C-bus byte write accesses will define several
characters.
8.11.3 OSD CHARACTER MATRIX
Two different font sizes are supported; 24 × 24 and
12 × 16 pixels. With the internal matrix memory
42 characters (24 × 24 pixels) can be defined, or
128 characters (16 × 12 pixels).
The definition of the characters is achieved by writing to
registers 200 and 201 (see Table 7). The first register
must be written to with the character code of the character
to be defined. Then the bytes with the pixel pattern must
be written to address 201 (see Table 7). The definition of a
character is done with 3 bytes per line at 24 × 24 font
(72 bytes per character), and with 3 bytes per 2 lines at
12 × 16 font (24 bytes per character), see Fig.21.
1999 May 11
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