AL250 International Power Sources, Inc., AL250 Datasheet - Page 14

• Manufacturer Part Number: AL250
• Description: Video Scan Doubler
• Manufacturer: International Power Sources, Inc.

6.5 OSD Interface
The AL250/251 provides two ways to implement the on screen display. The internal way is to
program the built-in on-screen display (OSD) bitmap, and the external way is to control the two
overlay pins for showing on screen display or creating special effects onto each single pixel on screen.
The AL250/251 provides 256 registers to implement the two internal bitmaps, which are
programmable as 16x16 blocks (4x4 pixels each) and 48x16 blocks (8x8 pixels each) respectively.
To program the OSD, first use LUT/OSD Control register 10h to turn on bitmap 1 or bitmap 2. Then
program the overlay colors 1, 2 and 3 through registers 15h~1Dh. Select the OSD index (0~255)
through register 11h, then fill the data through register 13h. The two bits of each OSD block can be
used to define no overlay color (transparent) or color 1, 2 or 3. Mesh color and mesh background can
be enabled by programming register 2Fh. The position of the bitmaps can be defined by registers
1Eh, 1Fh, and 2Fh.
The data index of the bitmap 1 starts at bitmap address 192, and the lay-out is defined as follows:
Each pixel is defined by 2 bits value (“00”, “01”, “10” and “11”).
Value “00” shows the current input video data.
Value “01”, “10” and “11” are index to overlay color 1~3 (defined in registers 15h ~ 1Dh).
The data index of bitmap 2 starts at bitmap address 0, and the lay-out is defined as follows:
192<7:0>
196<7:0>
200<7:0>
204<7:0>
252<7:0>
7:6 5:4 3:2 1:0
253<7:0>
193<7:0> 194<7:0> 195<7:0>
254<7:0> 255<7:0>
AL250-16
16x16 OSD drawing
July 28, 1999
AL250
14