ST92196A STMicroelectronics, ST92196A Datasheet - Page 120

• Manufacturer Part Number: ST92196A
• Description: 8/16-bit Mcu For Tv Applications With Up To 96k Rom, On-screen-display And 1 Or 2 Data Slicers
• Manufacturer: STMicroelectronics

OSD CONTROLLER (Cont’d)
8.5.3.11 Translucency Function
The translucency feature is designed to provide a
better OSD quality while displaying rows in mixed
mode.
Instead of forcing the background color of any
character to any full intensity color, (which will pre-
vent the viewer from seeing a significant amount of
the video picture), or having a fully transparent
background (i.e. no background) which makes the
OSD more difficult to read for the viewer, the trans-
lucency provides a real time mix between both the
video and the OSD background information. This
feature will appear as a “boxing” effect around all
the displayed characters.
The translucency can be handled in two different
ways at application level, depending on the video
processor used in the application.
1. When the video processor accepts an analog
2. When the video processor accepts only a digital
Figure 56. Digital Translucency Output Pin Example
TLSU Digital Output
control of the fast switch OSD signal (called
“FB”), the translucency can be handled directly
through the real time amplitude of the FB signal
(refer to Color attribute control for Border, Back-
ground palette and Underline color settings).
FB signal, the translucency function may be im-
plemented on the chassis with the help of an
additional digital output of the MCU, which is
provided as an I/O pin alternate function.
FB (active high)
Current displayed video line
Transparent Background
No Display
- ON SCREEN DISPLAY CONTROLLER (OSD)
This digital output called “TSLU” is active (set to
“1”) when the OSD displays the Background and
Foreground or when the mute is active (refer to the
description of the LSM[2:0] bits in the OSDMR reg-
ister) and is inactive the rest of the time (during
foreground or if no display), including character
00h.
This TSLU signal is controlled by the TSLE bit in
the OSDER register. When not used, (TSLE=0),
the TSLU signal is held at “1” by hardware.
Application Note
In order to enable the Translucency Function (See
Example No. 2, above), the following procedure
must be performed:
– Fast Blanking must be set to Digital mode. Set bit
– Initialize port 3.0 as a push-pull type Alternate
– Set bit TSLE (bit 2) of register OSDER (R248,
– For the selected colors (i.e. those which will ap-
A
Foreground
DIFB (bit 7) of register OSDBCR1 (R247, page
42) to 1. Refer to
tion.
Function output. Refer to
al
page 42) to 1. Refer to
Description.
pear as transparent with contrast reduction), set
bits BT[2:0] to 0. Refer to
ground
Description.
Palettes.
Section 8.5.9 Register Descrip-
Section 8.5.9 Register
Section 8.5.3 Function-
Section 8.5.6.4 Back-
No Display
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