Browse Prior Art Database

Smooth Scroll Using Dual Port DRAM

IP.com Disclosure Number: IPCOM000035122D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Asada, S: AUTHOR

Abstract

Disclosed is method for smooth scrolling an image on a display device, wherein the image data displayed on display lines of the display device are stored in an even buffer and an odd buffer, and the image data of the display lines are transferred between the even and odd buffers to perform the smooth scroll operations. Dual port DRAM (dynamic random- access memory) is used as the buffer.

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Smooth Scroll Using Dual Port DRAM

Disclosed is method for smooth scrolling an image on a display device, wherein the image data displayed on display lines of the display device are stored in an even buffer and an odd buffer, and the image data of the display lines are transferred between the even and odd buffers to perform the smooth scroll operations. Dual port DRAM (dynamic random- access memory) is used as the buffer.

As shown in a figure, the frame buffer comprises an even buffer 1 storing the image data of even lines of a display device 5 and an odd buffer 2 storing the image data of odd lines of the display device 5. Two dual port DRAMs are used as the even and odd buffers 1 and 2. In a normal display mode, both the serial ports 3 and 4 are set to a read mode to alternately access the buffers 1 and 2 to sequentially read out the lines 0, 1, 2, 3, etc. In both the normal and upward scroll modes, a two-line buffer 6 is not used.

In the upward scroll mode, the serial ports 3 and 4 are alternately switched between the read and write modes. During the display of the line 0, the serial port 3 is set to the read mode, so that the image data of the line 0 is supplied to the display device 5. During the display of the line 1, the serial port 4 is set to the read mode and the serial port 3 is set to the write mode, so that the image data of the line 1 is supplied to the display device 5 and is also supplied to the serial port 3 which writes the image data of the line 1 into the line address 0, whereby the image data of the line 0 in the even buffer 1 is replaced by the image data of the line 1 stored in the odd buffer 2. During the display of the line 2, the serial port 3 is set to the read mode and the serial port 4 is set to the write mode, so that the image date of the line 2 is supplied to the display device 5 and is also supplied to the serial port 4, so that the image data of the line 1 is replaced by the image data of the line 2. The replacements of the image data between the even and odd buffers 1 and 2 are repeated during the display of the image data. In the nex...