Display Architecture:-

The first Figure (given below) shows the display assembly on a PC-compatible system. The graphics controller that is part of the North Bridge connects to different types of display devices using several interface standards. Video Graphics Array (VGA) is the original display standard introduced by IBM, but it's more of a resolution specification today. VGA refers to a resolution of 640x480, whereas newer standards such as eXtended Graphics Array (XGA) and Super Video Graphics Array (SVGA) support higher resolutions of 800x600 and 1024x768. Quarter VGA (QVGA) panels having a resolution of 320x240 are common on embedded devices, such as handhelds and smart phones.



(Display connection on a PC system.)

Graphics controllers in the x86 world compatible with VGA and its derivatives offer a character-based text mode and a pixel-based graphics mode. The non-x86 embedded space is non-VGA, however, and has no concept of a dedicated text mode.

Embedded SoCs usually have an on-chip LCD controller, as shown in the second Figure (given below). The output emanating from the LCD controller are TTL (Transistor-Transistor Logic) signals that pack 18 bits of flat-panel video data, six each for the three primary colors, red, green, and blue. Several handhelds and phones use QVGA-type internal LCD panels that directly receive the TTL flat-panel video data sourced by LCD controllers.



(Display connection on an embedded system.)

The embedded device, as in the third Figure (given below), supports dual display panels: an internal LVDS flat-panel LCD and an external DVI monitor. The internal TFT LCD takes an LVDS connector as input, so an LVDS transmitter chip is used to convert the flat-panel signals to LVDS. An example of an LVDS transmitter chip is DS90C363B from National Semiconductor. The external DVI monitor takes only a DVI connector, so a DVI transmitter is used to convert the 18-bit video signals to DVI-D. An I2C interface is provided so that the device driver can configure the DVI transmitter registers. An example of a DVI transmitter chip is SiI164 from Silicon Image.



(LVDS and DVI connections on an embedded system.)