SAA6721E Datasheet, PDF (56/72 Pages) NXP Semiconductors – SXGA RGB to TFT graphics engine

Philips Semiconductors
SXGA RGB to TFT graphics engine
Preliminary specification
SAA6721E
If the colour correction unit is switched to bypass mode
(when colour_correction_on is not asserted), the incoming
colours are used for further processing.
Writing to the colour correction table is possible during
data processing.
The programming registers osd_v_size and osd_h_size
define the OSD window size in characters. The window
position inside the output frame must be defined with
osd_v_offset and osd_h_offset (see Fig.20).
8.11 On screen display
8.11.1 OSD GENERALS
The implemented OSD is a character based window
system. It consists of a character matrix memory where all
character definitions are stored, and an OSD window
memory defining the OSD window’s contents. The OSD
window will be inserted into the video data stream if
osd_active is set to logic 1. Writing to these memories can
be done during data processing.
8.11.2 OSD WINDOW
The OSD window contains the character, colour and
appearance information to be displayed. Such a definition
exists for each character position. A character can use one
of 8 different foreground and background colours. Some of
these colours can be defined as transparent colours where
the original picture information will be displayed instead,
as alpha blended colours where a 1 : 1 or 1 : 2 alpha
blending will be done between picture and OSD, or as
normal colours. Transparency or alpha blending effects
will be enabled or disabled for the single characters.
The size and outline of the visible OSD window can be
programmed as long as the internal memory meets the
needs. This memory is able to store information of
1152 characters information.
handbook, halfpage
osd_v_offset
osd_h_offset
osd_v_size
OSD
OUTPUT FRAME
osd_h_size
MHB260
Fig.20 OSD window positioning.
The OSD can be programmed to use a 24 × 24 character
matrix, or a 12 × 16 matrix. The first one should be used for
Kanji and the second for standard characters.
The selection of the font size is done by char_size.
A logic 1 selects 24 × 24 font, and a logic 0 the smaller
12 × 16 font. If the small 12 × 16 font is used, up to
128 different characters can be defined. Alternatively up to
42 characters of the larger 24 × 24 font can be used.
Table 18 gives some possible OSD settings.
1999 May 11
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