What does the VGA Adapter do?

The VGA Adapter is a hardware module designed for the Altera DE2 board to control video display in a 640 by 480 resolution. The adapter provides a simple interface to draw pixels on a monitor screen, without the need to fully comprehend the VGA signalling standard necessary to actually transmit each pixel to a monitor. The adapter stores the location and colour of each pixel in its internal memory and then updates the image on a monitor approximately every 60th of a second. A block diagram of the adapter is shown below.

Because of the limit of on-chip memory on the Altera DE2 board (~500k bits) a full 640 by 480 resolution with more than a two colours is not feasible, hence we reduce the resolution available to the user to one of 320x240 and 160x120. Instead of a resolution of 640 by 480 pixels, the screen is divided into 320/160 columns and 240/120 rows of Mega Pixels.

Mega Pixels

Mega Pixels are 2/4 pixels wide and 2/4 pixels high. Because of this difference, the resolution is 320x240 (or 160x120) instead of 640x480 (the VGA Resolution). The figure below demonstrates how these Mega Pixels are represented on the monitor when working in a 160x120 MegaPixel mode.

To light up a specific MegaPixel on the screen the user simply specifies the (x, y) coordinates and its colour to the adapter. The adapter then updates its internal memory and displays the new image during the next screen update cycle.

Interface

The "VGA Adapter's Interface" page outlines all of the details involved with the VGA Adapter module and explains how to use the VGA Adapter module. You can use that page as a quick future reference to obtain relevant details about the module.