Display system for plural display areas on one screen

• US 4,903,013 A
• Filed: 12/30/1987
• Issued: 02/20/1990
• Est. Priority Date: 01/07/1987
• Status: Expired due to Fees

• Current Assignee: Brother Kogyo Kabushiki Kaisha (Brother Industries Limited)
• Original Assignee: Brother Kogyo Kabushiki Kaisha (Brother Industries Limited)
• Inventors: Takeda, Susumu
• Primary Examiner(s): Brigance, Gerald
• Assistant Examiner(s): HJERPE, RICHARD A
• Application Number:
  US07/139,809
• Time in Patent Office: 783 Days
• Field of Search: 340/721, 340/723, 340/724, 340/726, 364/521
• US Class Current: 345/686
• CPC Class Codes: G09G 1/007 Circuits for displaying split screens

Abstract

A display system for displaying characters on a screen which is divided into a plurality of display areas and for allowing a scroll within each of the display areas with one chip of display data RAM without image confusion between the display area. The display data RAM is also divided into plural areas corresponding to the display areas. This system includes address conversion circuit provided between a display controller and the display data RAM for converting a virtual address outputted from the display controller into an actual address of the display data RAM. Here the virtual address is an address out of actual address of the display data RAM.

Claims

1. A display system for displaying characters on a screen which is divided into a plurality of display areas and for allowing a scroll within each of the display areas, comprising:

display data memory means for storing character data to be displayed on the screen, the display data memory means being divided into a plurality of memory areas each corresponding to a respective display area;

display control means for sequentially outputting addresses in order to output the character data of the display data memory means designated by the addresses to each of the display areas of the screen corresponding to respective memory areas of the display data memory means,

wherein a first number of address designation lines of the display control means is greater than a second number of address designation lines of the display data memory means; and

address conversion means including a logic circuit provided between the display control means and the display data memory means for converting said first number of addresses outputted from the display control means into said second number of addresses of the display data memory means, said logic circuit receiving a select number of said first number of address designation lines and outputting less than said select number of said second number of address designation lines, whereby any virtual address outputted from said display control means is converted into an actual address of the memory areas of the display data memory means, the virtual address being greater than any of the actual addresses of the display data memory means.

2. A display system for displaying characters on a screen which is divided into a plurality of display areas and for allowing a scroll within each of the display areas, comprising:

display data memory means for storing character data to be displayed on the screen, the display data memory means being divided into a plurality of memory areas each corresponding to a respective display area;

display control means for sequentially outputting addresses in order to output the character data of the display data memory means designated by the addresses to each of the display areas of the screen corresponding to respective memory areas of the display data memory means,

wherein a first number of address designation lines of the display control means is greater than a second number of address designation lines of the display data memory means; and

address conversion means provided between the display control means and the display data memory means for converting said first number of addresses outputted from the display control means into said second number of addresses of the display data memory means whereby any virtual address outputted from said display control means is converted into an actual addresses of the memory means of the display data memory means, the virtual address being greater than any of the actual addresses of the display data memory means,

said address conversion means including a logic circuit receiving inputs of a select number of said first number of address designation lines and outputting less than said select number of said second number of address designation lines; and

control means for outputting a start address and an amount of following addresses designating a part of an area of the display data memory means to the display control means in order to display characters of the part and for rewriting contents of the display data memory means and shifting the start address by an amount corresponding to one line for scrolling the display area of the screen by one line.

3. The display system according to claim 2, wherein when the start address is a virtual address, the control means changes the start address from the virtual address to the actual address corresponding to the virtual address.