Basic Video Controller Refresh Operations

✓ The basic refresh operations of the video controller are diagrammed

✓ Two registers are used to store the coordinate values for the screen pixels

✓ Initially, the x register is set to 0 and the y register is set to the value for the top scan line.
✓ The contents of the frame buffer at this pixel position are then retrieved and used to set the intensity of the CRT beam.
✓ Then the x register is incremented by 1, and the process is repeated for the next pixel on the top scan line.
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✓ This procedure continues for each pixel along the top scan line.
✓ After the last pixel on the top scan line has been processed, the x register is reset to 0 and the y register is set to the value for the next scan line down from the top of the screen.
✓ The procedure is repeated for each successive scan line.
✓ After cycling through all pixels along the bottom scan line, the video controller resets the registers to the first pixel position on the top scan line and the refresh process starts over.