©2006 Copyright by AverLogic Technologies, Corp. Version 1.0 1
1. Introduction
1.1. Introduction
The AL251A-EVB-A0 is an engineering evaluation board that is used to
evaluate and demonstrate the performance of the AL128 VGA to TV scan
converter chip and AL251 TV to VGA scan converter chip. The board contains
two 3M bits of field memory (AL422B) for AL128, and one video decoder
(AL242) for AL251. An attached 80C51 microcontroller is used to control AL242
and AL251 via 2-wire Serial Bus.
The evaluation board accepts VGA analog signals or analog video signals.
AL128 converts the analog VGA signal into NTSC/PAL S-video and composite
video (CVBS), or analog RGB for SCART application. Additional bypass VGA
output could be added via the video buffer. This implementation can display at
both the monitor and TV simultaneously. Through AL251 and AL242, it accepts
NTSC/PAL S-video or composite video (CVBS) and converts into VGA analog
signal output or 16-bits
digital RGB/YUV output.
Various switches and buttons are designed in the evaluation board for ease of
demonstrating and testing the functions. For detailed descriptions of each
connector, button and LED, please refer to “Block diagram and settings” section.
The board uses an external DC power adaptor (+12V/1A).
1.2. Product Overview
1.2.1. AL128
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Converts non-interlaced VGA into interlaced TV format (NTSC/PAL)
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Composite video
and S-Video outputs
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Analog RGB output for SCART interface
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Highly integrated design with built-in NTSC/PAL encoder, ADC, DAC and SRAM
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High clarity 5-line anti-flicker filter
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8 levels of sharpness control
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Supports up to full 1024x768 VGA resolution
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Automatically supports scan rate from 50 Hz up to 100 Hz
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Linear vertical and horizontal overscan/underscan control
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Zoom and freeze controls
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Four-touch-button interface with OSD (on TV) to control all key functions
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Picture panning control
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Brightness control
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Built-in color bar
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Simultaneously displays on PC and TV monitors
1.2.2. AL251
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Converts interlaced TV signal (NTSC/PAL) into non-interlaced RGB format for
CRT monitorsor LCD panels
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Highly integrated design with built-in DAC,SRAM, OSD and LUT
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Built-in on-screen-display with programmable bitmap
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Auto NTSC/PAL detection
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Analog/digital non-interlaced RGB (VGA) signal output (Scan Doubled or
