ASX340AT Datasheet, PDF (42/75 Pages) ON Semiconductor – Color CMOS NTSC/PAL Digital Image

ASX340CS: 1/4-Inch Color CMOS NTSC/PAL Digital Image Sensor
Overlay Capability
Overlay Capability
Figure 23 highlights the graphical overlay data flow of theASX340AT. The images are
separated to fit into 2 KB blocks of memory after compression.
• Up to four overlays may be blended simultaneously
• Overlay size 360 x 480 pixels rendered into a display area of 720 x 480 pixels (NTSC) or
720 x 576 (PAL)
• Selectable readout: rotating order is user programmable
• Dynamic movement through predefined overlay images
• Palette of 32 colors out of 64,000 with eight colors per bitmap
• Blend factors may be changed dynamically to achieve smooth transitions
The host commands allow a bitmap to be written piecemeal to a memory buffer through
the two-wire serial interface, and also through DMA direct from SPI Flash memory.
Multiple encoding passes may be required to fit an image into a 2KB block of memory;
alternatively, the image can be divided into two or more blocks to make the image fit.
Every graphic image may be positioned in the horizontal and vertical direction and
overlap with other graphic images.
The host may load an image at any time. Under control of DMA assist, data are trans-
ferred to the off-screen buffer in compressed form. This assures that no display data are
corrupted during the replenishment of the four active overlay buffers.
Figure 23: Overlay Data Flow
Flash
Bitmaps - compressed
Overlay buffers: 2KB each
Off-screen
buffer
Decompress
Blend and Overlay
Note: These images are not actually rendered, but show conceptual objects and object blending.
ASX340AT/D Rev. H, 8/15 EN
42
©Semiconductor Components Industries, LLC, 2015.