Raster scan type CRT display system having an image rolling function
First Claim
1. A raster scan type CRT display system having an image rolling function wherein coded data stored in a refresh memory is read out in synchronism with the scan of a CRT display and is displayed on a CRT viewer in accordance with a sequence of display column and row addresses, said CRT viewer having a display capacity of m columns by n rows and said refresh memory can be accessed by a processor for read/write operation, said display system comprising:
- said refresh memory being randomly accessable and having a storage capacity of at least m x n characters;
a timing control circuit for generating timing signals which include character clock pulses and line clock pulses;
column and row start address registers for defining a read start address for said refresh memory;
column and row cursor address registers for defining an address for the read/write operation by said processor to said refresh memory;
a modulo m address counter to which the content of said column start address register is preset for each horizontal scan and which counts up the character clock pulses from said timing control circuit starting from the preset count to produce a sequence of display column addresses; and
a modulo n address counter to which the content of said row start address register is preset for each vertical scan and which counts up the line clock pulses from said timing control circuit starting from the preset count to produce a sequence of display row addresses.
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Accused Products
Abstract
A raster scan type CRT display system is disclosed which has a randomly accessable refresh memory. The display system comprises column and row start address registers for defining a read start address for the refresh memory, column and row address counters for counting the contents of the column and row start address registers as start positions to generate a read address of the refresh memory for display, column and row cursor registors for defining a data entry position on a CRT screen, and column and row address generators for generating an entry address for the refresh memory based on the contents of the column and row start address registers and the contents of the column and row cursor registers, whereby a rolling or shifting of the image is effected and the refresh memory can be accessed by a processor for read/write operation without the need to monitor the image rolling.
37 Citations
5 Claims
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1. A raster scan type CRT display system having an image rolling function wherein coded data stored in a refresh memory is read out in synchronism with the scan of a CRT display and is displayed on a CRT viewer in accordance with a sequence of display column and row addresses, said CRT viewer having a display capacity of m columns by n rows and said refresh memory can be accessed by a processor for read/write operation, said display system comprising:
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said refresh memory being randomly accessable and having a storage capacity of at least m x n characters; a timing control circuit for generating timing signals which include character clock pulses and line clock pulses; column and row start address registers for defining a read start address for said refresh memory; column and row cursor address registers for defining an address for the read/write operation by said processor to said refresh memory; a modulo m address counter to which the content of said column start address register is preset for each horizontal scan and which counts up the character clock pulses from said timing control circuit starting from the preset count to produce a sequence of display column addresses; and a modulo n address counter to which the content of said row start address register is preset for each vertical scan and which counts up the line clock pulses from said timing control circuit starting from the preset count to produce a sequence of display row addresses. - View Dependent Claims (2, 3, 4)
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5. A raster scan type CRT display system wherein coded data stored in a refresh memory is read out in synchronism with the scan of a CRT display and is displayed on a CRT viewer having a display capacity of m columns by n rows and said refresh memory can be accessed by a processor for read/write operation, said display system comprising:
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said refresh memory having a storage capacity of at least m x n characters; a timing control circuit for generating timing signals which include character clock pulses and line clock pulses; column and row start address registers for defining a read start address for said refresh memory; said processor connected to said CRT display system through an interface to access to said refresh memory for the read/write operation; a keyboard for issuing a read/write command to said processor through said interface; column and row cursor address registers for defining an address for the read/write operation by said processor to said refresh memory; a modulo m address counter to which the content of said column start address register is preset for each horizontal scan and which counts up the character clock pulses from said timing control circuit starting from the preset count to produce a sequence of display column addresses; a modulo n address counter to which the content of said row start address register is preset for each vertical scan and which counts up the line clock pulses from said timing control circuit starting from the preset count to produce a sequence of display row addresses; first adders for summing the contents of said column and row cursor address registers with the contents of said column and row start address registers respectively; comparators for comparing the respective outputs of said first adders with the numbers m and n of the horizontal and vertical displayed characters respectively, to produce "1" outputs when the respective output of said first adders is equal to or greater than m or n respectively; complementers for producing complement outputs of the numbers m and n of the horizontal and vertical displayed characters only when the respective output of said comparators is "1"; second adders for summing respective outputs of said first adders with the respective outputs of said complementers to produces the read/write address; a character generator for generating a character signal corresponding to coded data read from said refresh memory; a parallel-serial converter for converting the parallel character signal from said character generator to a serial character signal; and said CRT viewer having a display capacity of m columns by n rows.
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Specification