Cursor circuit for a dual port memory

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(11)

EP 0 229 986 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	27.12.1989 Bulletin 1989/52

(43)	Date of publication A2:
	29.07.1987 Bulletin 1987/31

(21)	Application number: 86117314.4

(22)	Date of filing: 12.12.1986

(51)	International Patent Classification (IPC)⁴: G09G 1/00

(84)	Designated Contracting States:
	DE FR GB IT

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Priority:

17.01.1986 US 820487

(71)	Applicant: International Business Machines Corporation
	Armonk, N.Y. 10504 (US)

(72)	Inventors:
	Muhich, John Stephen Austin Texas (US) Thornley, Joseph Stoddard Round Rock Texas 78681 (US)

(74)	Representative: Burt, Roger James, Dr.
	IBM United Kingdom Limited Intellectual Property Department Hursley Park Winchester Hampshire SO21 2JN Winchester Hampshire SO21 2JN (GB)

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References cited: :

(54)	Cursor circuit for a dual port memory

(57) A cursor generation circuit for an image display system that includes a storing circuit 1 for storing image data. The storing circuit includes a first port 8 to provide access to the image data to the display system and a second port 12 to provide access to the image data to a display device 10 for displaying the image data. A combining circuit 22 is further provided to combine the image data with cursor data in the storing circuit when the storing circuit is being accessed by the display device. However, the combin- ing circuit removes the cursor data from the image data when the image data is being accessed by the display system through the first port.

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