ST92185B STMicroelectronics, ST92185B Datasheet - Page 88

• Manufacturer Part Number: ST92185B
• Description: 16k/24k/32k Rom Hcmos Mcu With On-screen-display
• Manufacturer: STMicroelectronics

ST92185B - ON SCREEN DISPLAY (OSD)
7.4 ON SCREEN DISPLAY (OSD)
7.4.1 Introduction
The OSD displays Teletext or other character data
and menus on a TV screen.
In serial mode, characters are coded on one byte.
The display is fully compliant with the WST Tele-
text level 1.5.
In parallel mode, characters are coded on two
bytes, one byte being the font address (character
code), the second byte being used for attribute
control, which can be combined with the serial at-
tribute capabilities. In this mode, the display meets
a significant part of the WST Teletext level 2 spec-
ification.
In order to save memory resources (reduce sys-
tem cost), two display modes are provided with ei-
ther a page mode display mode (teletext stan-
dard, 26 rows) or a line mode (up to 12 rows) for
non teletext specific menus.
The OSD is seen by the ST9 as a peripheral which
has registers mapped in the Paged Register
space.
The character codes to be displayed are taken
from the TDSRAM memory. They are addressed
by the display with the real time sequencer
through the TDSRAM interface character by char-
acter.
The font ROM contains 512 characters. The stan-
dard European font contains all characters re-
quired to support Eastern and Western European
languages. Each character can be defined by the
user with the OSD Screen/Font Editor. All fonts
(except the G1 mosaic font) are fully definable by
masking the pixel ROM content.
Display is done under control of the ST9 CPU and
the vertical and horizontal TV synchro lines.
The OSD provides the Red, Green, Blue signals
and the Fast Blanking switching signal through
four analog outputs. The three Color outputs use a
3-level DAC which can generate half-intensity col-
ors in addition to the standard saturated colors.
The Display block diagram is shown on
88/178
Figure
1.
A smart pixel processing unit provides enhanced
features such as rounding or fringe for a better pic-
ture quality. Other smart functions such as true
Scrolling and cursor modes allow designing a high
quality display application.
7.4.2 General Features
(SH: Single Height, SW: Single Width, DH: Double
Height, DW: Double Width, DS: Double Size)
DH x SW = 20 * 10 dots
Serial Character Mode supporting Teletext level
1.5
Parallel Character Mode for TV character
displays (for example channel selection or
volume control menus)
40 or 80 characters/row
Full Page Mode:
23 rows plus 1 Header and 2 Status Rows
Line Mode:
Up to 12 rows plus 1 Header and 2 Status Rows.
4/3 or 16/9 screen format
Synchronization to TV deflection, by Hsync and
Vsync or Csync.
Box Mode: Display text inside and outside box
solid, transparant or blank
Rounding and Fringing
Cursor Control
Concealing
Scrolling
Semi-transparent mode (text windowing inside
video picture)
Half-Tone mode (reduces video intensity inside
a box)
Normal character size 10 x 10 dots.
Other character sizes available as follows:
SH x SW = 10 * 10 dots
Both Serial and
Parallel Mode
Parallel Display Mode
SH x DW = 10 * 20 dots
DS=DH x DW = 20 * 20
only
dots