videocont - Massachusetts Institute of Technology...

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Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science 6.111 - Introductory Digital Systems Laboratory Using the MC6847 Video Controller Brief Description The 6847 is a video display controller. It reads data from a RAM or PROM, converts this data to a pattern of dots (pixels or pels), and generates the correct video signal to send to a video monitor. The 6847 can provide color or monochrome displays in a variety of resolutions. It can also display text data in some graphics modes. The 6847 also generates synchronization signals for the TV monitor. MC6847 data sheet: See p. 15, Figure 17a The selected mode determines the display characteristics. This mode defines the size, number, and sometimes the color of the display elements. It determines the number of memory locations read and how the data is interpreted. The mode is specified by nine inputs to the 6847. Choose an appropriate mode for your project display requirements, you don't have to use every available feature of the MC 6847! Text or Graphics The 6847 can be used for text or graphics. In the text modes, the screen contains 16 rows, each containing 32 characters. Each position corresponds to a location in display memory. Memory addresses 00 - 1F contain the data for the first row, 20 - 3F for the second row, etc. The displayed character is determined by the value stored in memory. You can use an external PROM or the internal ROM to create the character images. In the graphics modes, the display is made up of an array of boxes, each box being off or on. Each box is controlled by one or more bits in display memory. Text and graphics can be mixed by changing the mode ``on the fly". This is accomplished by defining the G/A input as a logical function of the 6847's address lines. Resolution
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videocont - Massachusetts Institute of Technology...

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