Virtual memory hardware cusor and method

Abstract

A hardware cursor is implemented on a typical video display controller, and uses an unused portion of video RAM as cursor memory to store the cursor information. Since the cursor memory may be located at any unused location of video RAM, it is a virtual hardware cursor since the location of cursor data may changed as required. The operation of the cursor may be programmed, monitored and controlled via control registers. The hardware cursor monitors the video control signals to determine when to put out cursor data rather than directly outputting pixel data. The hardware cursor fetches the appropriate cursor data from the cursor memory in the video RAM during the horizontal nondisplay period just prior to a line of display data that should contain cursor data. The hardware cursor then monitors the pixel stream and outputs unchanged pixel data until a cursor location is reached, at which time the hardware cursor outputs a logical combination of cursor data, cursor color, and pixel value. The logic of the hardware cursor thus dynamically changes the pixel value to make the cursor appear on the video display monitor without requiring the video controller software to perform the data manipulations and transfers for the cursor.