VGA Input

VGA, or Video Graphics Array, is a standard for Video transmission using analog signals. Early CRT displays could only receive analog signal input due to design and manufacturing reasons, so the video card inside the computer was responsible for digital-to-analog conversion, and the VGA Interface was the interface for the output of analog signals on the video card. Today, LCD monitors can receive digital signals directly, but in order to be compatible with VGA interfaces on video CARDS, VGA standards are mostly supported.

In VGA video transmission standard, the video image is decomposed into red, green and blue primary color signals. After digital-to-analog conversion, the video image is transmitted in three independent channels under the synchronization of HSYNC and VSYNC signals. The synchronization timing of VGA in the transmission process is divided into line timing and field timing. VGA timing consists of three elements: pixel clock, row field synchronization signal, and image data.

Early VGA specifically refers to the Resolution of 640X480 display mode, later, according to the resolution, VGA is divided into VGA (640X480), SVGA (800x600), XGA (1024x768), SXGA (1280x1024), etc. VGA display timing at different resolutions is similar