Importance

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Abstract

A display controller displays an image on either of a CRT display unit and a liquid crystal display unit (LCD) having upper and lower screens in accordance with image data stored in a memory. When a CRT display unit is driven, an address generating circuit calculates at the beginning of each horizontal scanning an address of the memory corresponding to the leftmost display position on the current horizontal scanning line in accordance with the vertical position of the horizontal scanning line and the number of display positions on a horizontal scanning line, and stores data representing the address in a first register. The data in the first register is incremented in accordance with the horizontal scanning and fed to the memory to read the image data. When the LCD is driven, the address generating circuit calculates at the beginning of each horizontal scanning two addresses of the memory corresponding respectively to the left most display positions on the current horizontal scanning lines on the upper and lower screens. In this case, the first one is obtained in accordance with the vertical position of the current horizontal scanning line on the upper screen and the number of display positions on a horizontal scanning line, while the second one is obtained by adding the number of display positions on the upper screen to the calculated first address.

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First Claim