Apparatus for controlling a scanning type video display to be divided into plural display regions
First Claim
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1. An apparatus for controlling a scanning type video display, comprising:
- a video memory for storing image data;
a group of registers for storing control data for accessing said video memory, said registers including (a) an address register for storing an address value corresponding to an address of a selected one of the remaining ones of said group of registers, and (b) a raster setting register for designating an interrupt raster number;
counter means for counting a current raster number of said video display;
comparator means for comparing said interrupt raster number of said raster setting register and said current raster number and, in response to said numbers being equal, generating a coincidence signal; and
means for controlling said video display in response to said control data, including(a) means for storing in said address register an address value corresponding to said raster setting register whereby said raster setting register is selected from said groups of registers to store a raster number,(b) means for sequentially storing a set of raster numbers in said raster setting register whereby a raster number stored in said raster setting register is replaced by a next larger raster number in response to said coincidence signal and plural coincidence signals are generated sequentially in response to the renewal of said one of said plural raster numbers, and(c) means for dividing said video display into plural display regions in response to said plural coincidence signals whereby images are displayed on said plural display regions of said video display in response to said image data.
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Abstract
An apparatus for controlling the access of a video memory comprises a group of registers in which various kinds of control data are set to access a video memory. The group of the registers are set to store data for detecting scanning rasters, incrementing or decrementing an address of the video memory which is accessed, and starting a DMA transfer of image data. Therefore, various kinds of accessing modes can be performed without the necessity of a complicated software.
28 Citations
9 Claims
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1. An apparatus for controlling a scanning type video display, comprising:
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a video memory for storing image data;
a group of registers for storing control data for accessing said video memory, said registers including (a) an address register for storing an address value corresponding to an address of a selected one of the remaining ones of said group of registers, and (b) a raster setting register for designating an interrupt raster number;counter means for counting a current raster number of said video display; comparator means for comparing said interrupt raster number of said raster setting register and said current raster number and, in response to said numbers being equal, generating a coincidence signal; and means for controlling said video display in response to said control data, including (a) means for storing in said address register an address value corresponding to said raster setting register whereby said raster setting register is selected from said groups of registers to store a raster number, (b) means for sequentially storing a set of raster numbers in said raster setting register whereby a raster number stored in said raster setting register is replaced by a next larger raster number in response to said coincidence signal and plural coincidence signals are generated sequentially in response to the renewal of said one of said plural raster numbers, and (c) means for dividing said video display into plural display regions in response to said plural coincidence signals whereby images are displayed on said plural display regions of said video display in response to said image data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification