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Display Hardware Yingcai Xiao

Display Hardware Yingcai Xiao. Printers. Dot Size: dpi (dot per inch). 300, 600, 1200, … Dot Distance. Printers. Types : Dot-matrix: Printer head has 7x7 ~ 24x24 pins. Pen plotter: Drawing with mechanical pens.

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Display Hardware Yingcai Xiao

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  1. Display HardwareYingcai Xiao

  2. Printers Dot Size: dpi (dot per inch). 300, 600, 1200, … Dot Distance.

  3. Printers • Types: • Dot-matrix: Printer head has 7x7 ~ 24x24 pins. • Pen plotter: Drawing with mechanical pens.

  4. Laser printer: position-charged rotating drum, laser beam hits the parts to be white, discharge the areas, negatively charged powered toner adheres to the positively charged area.

  5. Ink-jet printer: sprays cyan, magenta, yellow and black ink onto paper.  • Thermal-transfer: Colored wax-paper ==> plain paper • Thermal-sublimation dye transfer: 256 intensities for each C, M, Y==>16M colors. Near-photographic • Camera • Film recorder

  6. Display Technologies 1) B/W CRT (Cathode Ray Tube): Cathode ray hits phosphor, which in turn emits light.

  7. Phosphor Persistence: time of decay after electronic excitation. (Can’t be too short or too long.) • Critical Fusion Frequency CFF > 60 frames/second. • Bandwidth of a monitor depends on how fast the electron gun can be turned on and off. n pixels / scan line ==> on/off n times per scan line 1000 pixels / line * 1000 line /frame * 60 frames / s  16 nanoseconds / switch.

  8. 2) Color CRT • 3 guns: RGB • Triad phosphor dots: RGB • One gun: Sony Trinitron (http://en.wikipedia.org/wiki/Trinitron)

  9. 3) Projection CRT (for large-screen) 4) LCD: liquid-crystal display (light weight) • raster, grid-like • lighting at point (x, y) changes when voltage is applied at the point. • Active Matrix: emitting light • Passive: reflecting light 5) LED: light-emitting diode (http://en.wikipedia.org/wiki/LED) 4) PDP: Plasma Display Panel http://en.wikipedia.org/wiki/Plasma_display

  10. Raster-Scan Display Systems A simple raster system

  11. The Video Controller The most important task for the controller is the constant refresh of the display (60 frame per second) 1) Interlaced 1st field: odd lines 2nd field: even lines 2) Non-interlaced: updates every scan-line in every field 3) Output: RGB, monochrome, NTSC (video tape) 4) Sprites in animation: a sequence of fixed-size pixel maps. 5) Video Mixing: 6) FB + External Video --> VC --> display

  12. Frame Buffer: memory that stores the color data for each pixel on the screen.Video controller reads the color value for each pixel and controls the intensity of the display at the pixel.

  13. Memory Speed Problem: 1K pixels / line  1K lines / frame  60frame / second  60 million reads/second ==>16 ns per read RAM speed ~ 50 ns/read ? Interlacing odd and even lines. VRAM: Video RAM (TI), reads all the pixels on a scan line in one cycle. Frame Buffer Depth Number of bits for each pixel (n). Also called number of planes. Number of possible colors: 2n

  14. VRAM size >= screen resolution * depth 24 bits: 16 M colors, True Color • 1K1K3 bytes =3MB VRAM • 1K7683=2.3MB • 8006003=1.5MB • 6404803=1MB 32 bits: RGBA, 16 M colors + Transparency (“Highest” in Windows) 16 bit: Pseudo True Color, 64K (“Medium” in Windows) • 1K1K2=2MB VRAM • 1K7682=1.5MB • 8006002=1 MB • 6404802=0.6 MB 8 bit: Indexed Color, 256, SVGA • 1K1K1=1MB VRAM • 8006001=0.5MB

  15. Look-up Table for Indexed Color With indexed colors, pixel values represent the index number into the LUT. The corresponding data value in the LUT represent the colors. • 8 bits / pixel => 256 colors at a time. • 12 bit / entry => 4k colors to chose the 256 from.

  16. GPU (Graphics Processing Unit) • Specialized hardware to assist graphics display operations. (scan-convert, bitblt) • More to come on GPU and GPGPU.

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