Digital Visual Interface (dvi)

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Digital Visual Interface (DVI).
As the data to be displayed on you screen is processed in your computer and graphics card digitally it has to be converted to analogue for your monitor. It goes from the your graphics cards frame buffer as digital data and then to the RAMDAC (Ramdom Access Memory Digital to Analogue Converter) to come out as an analogue signal.

This Analogue signal is then converted back to digital data inside your LCD digital screen. This gives rise to two possible stages that can cause corruption or loss of picture quality.

A group of companies called the Digital Display Working Group (DDWG) including such as Intel, Fujitsu & Silicon Image have agreed on a data signalling standard for digital interfacing called DVI.

This high-speed serial interface uses Transition Minimised Differential Signalling (TMDS) a technology of Silicon Image's PanelLink to send data to the monitor. Transition Minimised is the reduction of the number of high-to-low & conversely low-to-high signal swings while Differential is the method of transmitting the signal using a pair of complementary signals.

The system consists of a TMDS transmitter to encode and serially transmit the data to a TMDS receiver. Each link is made of three data channels for RGB information (0,1,2) along with a clock signal.

The "Copper Barrier" restricts the amount of data that can be sent down a single copper wire to about 165MHz or 165 million pixels per second. The encoder makes a single 10-bit TMDS encoded character which is then uncoded at the receiver TMDS. DVI also allows for a second TMDS link (3,4,5) which uses the same clock so that the bandwidth can be evenly divided between them and increasing the the total bandwidth available. Single link giving a bandwidth of 1.65Gbps.

 Analogue support as well with DVI.
DVI is able to support Analogue & Digital on a single interface. DVI-D (DVI-Digital, digital only). DVI-I (DVI-Integrated supports analogue as well).

On the DVI-I connector the 24 pins on the left are used for digital signals with one for the clock signal. The 4 pins & + cross hair pin are used to transmit the analogue signal. This DVI-I connector or universal connector is likely to replace the standard 15-pin VGA connector we are all accustomed to in the future.

 Last thoughts.
We hope this article has given you an idea of what goes into making LCD panels and the necessary digital connections. When it comes to buying an LCD screen you need to remember about the dead pixels. Check with the company you are buying from their policy of return. Anything up to 8 dead pixels seems to be a standard number before some companies and manufacturers will replace your LCD screen.

But which to buy. There is no denying it that modern LCD screens look really great and are much smaller but what about the price and output compared to CRT monitors. With the current price of CRT monitors you could either buy a large top of the range model or two good ones for the price of a single LCD screen with its poor colour quality, low contrast & fixed resolution.

If you are only working with documents as such in the office then an LCD screen is great, but when it comes to graphical display work and games then choose a top quality CRT monitor.


DVI connectors including DVI-D pinout, DVI-I pinout, DFP pinout, EVC pinout, DVI connector pinout explanation, DVI technical specifications, DVI specs.

  • DVI is the digital video interface computer standard developed by Silicon Image. It offers a simple Plug-and-Play method to connect your laptop computer to your projector.

  • This all-digital connection automatically optimizes your computer to work with your projector. You don't have to make pixel-lock adjustments to your projector, or resolution or color changes to your computer. DVI handles it all.

  • DVI also allows you to use advanced features in Microsoft Power Point, so you can use notes on your laytop's display while using the DVI port for your audience.

  • DVI comes in many different ‘flavors‘:

DVI-D is a digital ONLY connector. This is the leading connector standard for digital only connection.

DVI-I can support digital AND analog (RGB). The connector has a few more pins. Some display and graphics cards manufacturers are offering this connector type on their products, as opposed to separate manufacturers are not supporting analog connection.

DFP (MDR20) was the initial connector type specified by the Digital Flat Panel working group. Like DVI-D, this connector supports digital only. While this connector type is still used on some displays, it is being phased out.

EVC, or P&D, is another connector type that some manufacturers are using on their projectors. This connector is similar to the DVI-I connector, but is slightly larger in size. Like DVI-I, it supports analog and digital. Some manufactures use this same connector for USB.

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