Welcome to the FPGA Cookbook.
This is part of a new series of handy recipes to solve common FPGA development problems. Look out for more FPGA cookbook posts soon.
You Need Video Timings
To work with standard monitors and TVs you need to use the correct video timings. This recipe includes the timings for three common modes using analogue VGA, DVI or HDMI: 640x480, 1280x720, and 1920x1080 all at 60 Hz.
Feedback to @WillFlux is most welcome.
Video Signals in Brief
Video signals have two phases: drawing pixels and the blanking interval. The sync signals occur within blanking intervals; separated from pixel drawing by the front porch and back porch. Horizontal sync demarcates a line and vertical sync a screen. The following diagram illustrates the different parts of the display signal for 640x480 at 60Hz; the HD resolutions work in a similar way.
Video timings are a complex area with different specifications, for example Coordinated Video Timings includes four timing varients for common HD resolutions. The HD timings presented here are conservative values that should work with most displays.
The sync polarity in the following tables refers to whether sync pulses should be positive or negative. The memory values show how many kilobits (NOT bytes) of memory you need to store a single frame. The data rate is the required bandwidth for 24 bits-per-pixel with the included timings.
VGA 640x480 60Hz
The classic VGA display that works with analogue VGA monitors as well as most modern HD displays. You can usually get away with using 25 MHz as the pixel clock, which can be handy if you're using a simple divider to create the pixel clock. Arty VGA Graphics in Verilog Part 1 includes a Verilog design using this display mode.
EDID Name DMT0659 Aspect Ratio 4:3 Pixel Clock 25.175 MHz Pixel Time 39.72 ns Active Pixels 307,200 total 8-bit Memory 2,400 Kbits 32-bit Memory 9,600 Kbits Data Rate 0.60 Gbps Horizontal Timings Active Pixels 640 Front Porch 16 Sync Width 96 Back Porch 48 Blanking Total 160 Total Pixels 800 Sync Polarity neg Vertical Timings Active Pixels 480 Front Porch 11 Sync Width 2 Back Porch 31 Blanking Total 44 Total Pixels 524 Sync Polarity neg
VGA timings from Rick Ballantyne via Martin Hinner.
HD 1280x720 60Hz
The lowest of the common HD resolutions, 720P is widely supported and has relatively modest bandwidth requirements: an 8-bit 720P display requires less than 8 Mbits per frame. Note how the pixel clock of 720P is half that of 1080P (below): this simplifies your design if you need to support both resolutions.
EDID Name 720p Aspect Ratio 16:9 Pixel Clock 74.25 MHz Pixel Time 13.468 ns Active Pixels 921,600 total 8-bit Memory 7,200 Kbits 32-bit Memory 28,800 Kbits Data Rate 1.78 Gbps Horizontal Timings Active Pixels 1280 Front Porch 72 Sync Width 80 Back Porch 216 Blanking Total 368 Total Pixels 1648 Sync Polarity pos Vertical Timings Active Pixels 720 Front Porch 3 Sync Width 5 Back Porch 22 Blanking Total 30 Total Pixels 750 Sync Polarity pos
720P timings from monitor EDID.
HD 1920x1080 60Hz
The 1080P HDMI monitor or television has been the dominant specification for some years. If you're only going to support one resolution then 1920x1080 is a solid choice. A full 32-bit 1080P display requires just under 64 Mbits per frame.
EDID Name 1080p Aspect Ratio 16:9 Pixel Clock 148.5 MHz Pixel Time 6.734 ns Active Pixels 2,073,600 total 8-bit Memory 16,200 Kbits 32-bit Memory 64,800 Kbits Data Rate 3.56 Gbps Horizontal Timings Active Pixels 1920 Front Porch 88 Sync Width 44 Back Porch 148 Blanking Total 280 Total Pixels 2200 Sync Polarity pos Vertical Timings Active Pixels 1080 Front Porch 4 Sync Width 5 Back Porch 36 Blanking Total 45 Total Pixels 1125 Sync Polarity pos
1080P timings from monitor EDID.
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