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Introduction to VGA

Wei MiaoYuxuan Zhou

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VGA

• VGA = Video Graphics Array• Introduced by IBM in 1987, still using today• All points addressable• Transmitting analog signal

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• XGA (Extended Graphics Array)• UVGA(Ultra Video Graphics Array)• HVGA(Half-size VGA)• QVGA(Quarter VGA)• SVGA(Super Video Graphics Array)• SXGA(Super Extended Graphics Array)• SXGA+(Super Extended Graphics Array)• WVGA(Wide VGA)

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VGA Specifications

• 256 kB Video RAM• 16-color and 256-color paletted display modes.• Selectable 25.175 MHz or 28.322 MHz master clock• Maximum of 800 horizontal pixels• Maximum of 600 lines• Refresh rates at up to 70 Hz (Usually 60 Hz)• Vertical blank interrupt • Planar mode: up to 16 colors (4-bit planes)• Packed-pixel mode: 256 colors (Mode 13h)

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• Pin 1 RED Red video• Pin 2 GREEN Green video• Pin 3 BLUE Blue video• Pin 4 ID2/RES formerly Monitor ID bit 2, reserved since E-DDC• Pin 5 GND Ground (HSync)• Pin 6 RED_RTN Red return• Pin 7 GREEN_RTN Green return• Pin 8 BLUE_RTN Blue return• Pin 9 KEY/PWR formerly key, now +5V DC• Pin 10 GND Ground (VSync, DDC)• Pin 11 ID0/RES formerly Monitor ID bit 0, reserved since E-DDC• Pin 12 ID1/SDA formerly Monitor ID bit 1, I²C data since DDC2• Pin 13 HSync Horizontal sync• Pin 14 VSync Vertical sync• Pin 15 ID3/SCL formerly Monitor ID bit 3, I²C clock since DDC2

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• front porch : the delay between the end of the video data of a scan line and initial edge of the sync pulse.

• pulse width :the period of time that the sync signal is asserted

• back porch : the delay between when the final edge of the sync pulse and the first piece of data for the next scan line.

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VGA Basic Components

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• Sequencer• Graphics Controller• Attribute Controller• DAC• CRT Controller

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VGA Memory Organization

• Use only 16-bit addresses, but 256K ram• VGA uses planar instead of linear memory

organization• Chain-4 Memory Organization• Planar Memory Organization• Odd/Even Memory Organization

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The VGA color palette

• Contain 256 colors, choose from 218 colors. can arbitrary change the palette input

(63,0,0)

(0,0,63)

(0,63,0)

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Question?