EEL 3705 / 3705L Digital Logic Design Spring 2007 Instructor: Dr. Michael Frank Modules #90-99 (Extra Slides): Design Examples Module #91: VGA (Video Graphics Adapter) Color Video Driver Circuit 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006

FLEX 10K: VGA Graphics Programming Examples A Simple VGA Driver, Test Pattern Generator, and Character Generator for the FLEX 10K 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006

Primary Colors in Kindergarten, vs. in Digital Video Pigment color mixing You may have been taught in kindergarten that red, yellow, and blue are the so-called “primary colors”… and that all other colors can be produced by mixing these. This is somewhat true, when it comes to mixing of absorptive pigments (paints); red, yellow, and blue form a basis for the color space, such that many nice shades can be produced as weighted averages of them, by the mixing of pigments… But, when it comes to light emission (e.g., from a monitor), the true primary colors are red, green, and blue. This is because the eye’s three types of cones respond in the most discriminating way to light of these specific wavelengths… any perceived color can be produced by adding together (not averaging) these colors in different amounts. yellow green orange blue red purple Red light “on” Blue light on Green light on Emissive color mixing 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006

Retinal cone response curves & typical emissive RGB basis wavelengths video green (~550 nm) video blue (~450 nm) video red (~700 nm) 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006

M. Frank, EEL3705 Digital Logic, Fall 2006 A simple, generic variant of the old PC Video Graphics Adapter (VGA) standard Colors: 8 3 bits, with 1 bit each for red, green, blue 000 = black, 001= blue, 010 = green, 011 = blue + green = cyan, 100 = red, 101= red + blue = magenta, 110 = red + green = yellow, 111 = red + green + blue = white Display resolution: 640 pixels/row (horiz.) × 480 scan lines (vert.) Display update frequency: Usually ~30-60 Hz 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006

M. Frank, EEL3705 Digital Logic, Fall 2006 VGA Cable Pinouts (p.13) 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006

M. Frank, EEL3705 Digital Logic, Fall 2006 Video Scan Line Timing fclk = 25.175 MHz; tclk = 39.722 ns 782 tclk (p. 26) 142 tclk 95 tclk 806 tclk 32.02 µs = 806 tclk = 95 tclk = 48 tclk 640 tclk = 25.42 µs = 24 tclk 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006

Scan Line Timing Hardware 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006

M. Frank, EEL3705 Digital Logic, Fall 2006 Video Frame Timing trow = 32.022 µs 514 rows (p. 27) 34 rows 32 rows 11 rows 2 rows 525 rows 16.8 ms 15.37 ms 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006

M. Frank, EEL3705 Digital Logic, Fall 2006 Frame Timing Hardware 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006

Entire VGA Driver Schematic 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006

Example Test Circuit for VGA Driver Goal: Generate diagonal color test pattern Computed by formula: RGB2..0 = (row + col)6..4 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006

Photo of VGA CRT Monitor Screen Circuit works perfectly! Files are in VGA_example.zip on BB 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006

Circuit to Demonstrate RGB Color Mixing Project archive file: VGA_RGB_demo_v2.zip Under control of the first 3 DIP switches, Display a solid red rectangle filling the right half of the screen; display a solid green rectangle filling the bottom half of the screen; display a solid blue rectangle filling the middle ¼ of the screen. When multiple of these rectangles are turned “on” simultaneously, in the regions where they overlap, you can see the apparent colors that are produced by the various combinations of red, green, and blue light Each filled rectangle is generated by appropriate comparators acting on the x and/or y screen coordinates x ≥ 320 Is true on the right half of the screen y ≥ 240 Is true on the bottom half of the screen (160 ≤ x < 480) & (120 ≤ y < 360) Is true in the middle ¼ of the screen. Red rectangle Green rectangle Pushbutton inputs Blue rectangle subcircuit 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006

Output of VGA_RGB_demo Here is what the display looks like when DIP switches 1,2,3 are all “up” 9/19/2018 M. Frank, EEL3705 Digital Logic, Fall 2006