The AL251A-EVB-A0 is an engineering evaluation board that is used to demonstrate the performance of the AL128 VGA-to-TV scan
converter chip and AL251 TV-to-VGA scan converter chip. The board contains two 3Mbits of field memory (AL422B) for AL128, and one video decoder (AL242) for AL251. An attached 80C51 microcontroller is used to control the 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-bit digital RGB/YUV output.

Various switches and buttons are designed in the evaluation board for ease of demonstrating and testing the functions.

The board uses an external DC power adaptor (+12V/1A).

AL128 Features

• Converts non-interlaced VGA into interlaced TV format (NTSC/PAL)
• Composite video and S-Video outputs
• Analog RGB output for SCART interface
• Highly integrated design with built-in NTSC/PAL encoder, ADC, DAC and SRAM
• High clarity 5-line anti-flicker filter
• 8 levels of sharpness control
• Supports up to full 1024x768 VGA resolution
• Automatically supports scan rate from 50 Hz up to 100 Hz
• Linear vertical and horizontal overscan/underscan control
• Zoom and freeze controls
• Four-touch-button interface with OSD (on TV) to control all key functions
• Picture panning control
• Brightness control
• Built-in color bar
• Simultaneously displays on PC and TV monitors

AL251 Features

• Converts interlaced TV signal (NTSC/PAL) into non-interlaced RGB format for
  CRT monitorsor LCD panels
• Highly integrated design with built-in DAC,SRAM, OSD and LUT
• Built-in on-screen-display with programmable bitmap
• Auto NTSC/PAL detection
• Analog/digital non-interlaced RGB (VGA) signal output (Scan Doubled or Deinterlaced)
• Internal RGB video lookup table (LUT) to provide gamma correction and
  special effects
• Overlay support for title making and complex on-screen display
• 16-bit digital RGB/YUV output