Video Interface Palette (RAMDAC)



The TVP3026 is an advanced video interface palette (VIP) from Texas Instruments implemented in EPICE 0.2-micron CMOS process. The TVP3026 is a 64-bit VIP that supports packed-24 modes enabling 24-bit true color and high resolution at the same time without excessive amounts of frame buffer memory. For example, a 24-bit true color display with 1280 x 1024 resolution may be packed into 4M of VRAM. A PLL-generated, 50 % duty cycle reference clock is output in the packed-24 modes, maximizing VRAM cycle time and the screen refresh rate.

The TVP3026 supports all of the pixel formats of the TVP3020 VIP. Data can be split into 4 or 8 bit planes for pseudo-color mode or split into 12-, 16- or 24-bit true-color and direct-color modes. For the 24-bit direct color modes, an 8-bit overlay plane is available. The 16-bit direct- and true-color modes can be configured to IBM XGA (5, 6, 5), TARGA (1, 5, 5, 5), or 16-bit/pixel (6, 6, 4) configuration as another existing format. An additional 12-bit mode with 4-bit overlay (4, 4, 4, 4) is supported with 4 bits for each color and overlay. All color modes support selection of little or big endian data format for the pixel bus. Additionally, the device is also software compatible with the INMOSE IMSG176/8 and BrooktreeE Bt476/8 color palettes. Two fully programmable phase-locked loops (PLLs) for pixel clock and memory clock functions are provided, as well as a simple frequency doubler for dramatic improvements in graphics system cost and integration. A third loop clock PLL is incorporated making pixel data latch timing much simpler than with other existing color palettes. In addition, four digital clock inputs (2 TTL- and 2 ECL / TTL-compatible) may be utilized and are software selectable. The video clock provides a software selected divide ratio of the chosen pixel clock. The shift clock output may be used directly as the VRAM shift clock. The reference clock output is driven by the loop clock PLL and provides a timing reference to the graphics accelerator.

Like the TVP3020, the TVP3026 also integrates a complete IBM XGA-compatible hardware cursor on chip, making significant graphics performance enhancements possible. Additionally, hardware port select and color-keyed switching functions are provided, giving the user several efficient means of producing graphical overlays on direct-color backgrounds.

The TVP3026 has three 256-by-8 color lookup tables with triple 8-bit video digital-to-analog converters (DACs) capable of directly driving a doubly terminated 75-W line. The lookup tables are designed with a dual-ported RAM architecture that enables ultra-high speed operation. Sync generation is incorporated on the green output channel. Horizontal sync (HSYNC) and vertical sync (VSYNC) are pipeline delayed through the device and optionally inverted to indicate screen resolution to the monitor. A palette-page register is available to select from multiple color maps in RAM when 4 bit planes are used. This allows the screen colors to be changed with only one microprocessor write cycle.

The device features a separate VGA bus which supports the integrated VGA modes in graphics accelerator applications, allowing efficient support for VGA graphics and text modes. The separate bus also is useful for accepting data from the feature connector of most VGA-supported personal computers, without the need for external data multiplexing.

The TVP3026 is highly system integrated. It can be connected to the serial port of VRAM devices without external buffer logic and connected to many graphics engines directly. It also supports the split shift-register transfer function, which is common to many industry standard VRAM devices. The system-integration concept is even carried further to manufacturing test and field diagnosis. To support these, several highly integrated test functions have been designed to enable simplified testing of the palette and the entire graphics system.


  • Supports System Resolutions Up to 1600 × 1280 @ 76-Hz Refresh Rate
  • Supports Color Depths of 4, 8, 16, 24 and 32 Bit/Pixel
  • 64-Bit Wide Pixel Bus
  • Versatile Direct-Color Modes:
    • 24-bit/Pixel With 8-Bit Overlay (O, R, G, B)
    • 24-Bit/Pixel (R, G, B)
    • 16-Bit/Pixel (5, 6, 5) XGA Configuration
    • 16-Bit/Pixel (6, 6, 4) Configuration
    • 15-Bit/Pixel With 1 Bit Overlay (1, 5, 5, 5) TARGA Configuration
    • 12-Bit/Pixel With 4 Bit Overlay (4, 4, 4, 4)
  • True-Color Gamma Correction
  • Supports Packed Pixel Formats for 24 Bit/Pixel Using a 32-or 64-Bit/Pixel Bus
  • 50% Duty Cycle Reference Clock for Higher Screen Refresh Rates in Packed-24 Modes
  • Programmable Frequency Synthesis Phase-Locked Loops (PLLs) for Dot Clock and Memory Clock
  • Loop Clock PLL Compensates for System Delay and Ensures Reliable Data Latching
  • Versatile Pixel Bus Interface Supports Little- and Big-Endian Data Formats
  • 135-, 175-, and 220-MHz Versions
  • On-Chip Hardware Cursor, 64 × 64 × 2 Cursor (XGA and X-Windows Functionally Compatible)
  • Direct Interfacing to Video RAM
  • Supports Overscan for Creation of Custom Screen Borders
  • Color-Keyed Switching of Direct Color and True Color or Overlay
  • Hardware Port Select Switching Between Direct Color and True Color or Overlay
  • Triple 8-Bit D/A Converters
  • Analog Output Comparators for Monitor Detection
  • RS-343A Compatible Outputs
  • Direct VGA Pass-Through Capability
  • Palette Page Register
  • Horizontal Zooming Capability

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