ST92196A STMicroelectronics, ST92196A Datasheet - Page 124

• 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)
8.5.5 Programming the Display
The row-wise RAM buffer contains the description
of the characters to display:
– Row and character attributes (color, shape etc.)
– Horizontal shift code
– Character codes (addressing the Font ROM)
While one row buffer is displayed on the screen,
the CPU has time to prepare the content of the
next character row by filling up the second row
buffer. At the time the next row must be displayed,
the Display controller will point to the second row
buffer, allowing the CPU to start loading data into
the first row buffer for the following row. An inter-
rupt request is generated each time the buffer
pointer toggles.
Note: The display and the mouse share the same
interrupt line. In configurations with mouse, the
DINT and MOINT bits in the OSDFBR register can
be used to determine the interrupt cause.
The Vertical location of the next character row on
the screen is programmed by software through the
- ON SCREEN DISPLAY CONTROLLER (OSD)
Event Line value (Refer to
position of the beam is memorized by the Line
counter which counts the TV horizontal synchroni-
zation pulses (called here "Scan Line"). When the
Scan Line counter matches the Event Line value
the buffer toggle mechanism is activated.
8.5.5.1 OSDRAM Mapping
The OSDRAM is mapped in segment 22h of the
memory space.
In addition to row buffers, it is used to store color
palettes and information concerning mouse point-
er.
Note: The reset value of the OSDRAM contents is
undefined.
General Overview
The
DRAM mapping.
Figure 59
gives a general overview of the OS-
Figure
65). The vertical
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