Device for displaying characters and graphs in superposed relation

• US 4,491,832 A
• Filed: 02/01/1982
• Issued: 01/01/1985
• Est. Priority Date: 02/13/1981
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Tanaka, Kazuyuki
• Primary Examiner(s): Curtis, Marshall M.
• Application Number:
  US06/344,745
• Time in Patent Office: 1,065 Days
• Field of Search: 340/731, 340/749, 340/745, 340/721, 340/747, 340/814, 340/750, 340/744, 340/728, 340/735, 340/790
• US Class Current: 345/23
• CPC Class Codes: G09G 5/40 characterised by the way in which both a pattern determined by character code and another pattern are displayed simultaneously, or either pattern is displayed selectively, e.g. with character code memory and APA, i.e. all-points-addressable, memory

Abstract

A display device for displaying characters and graphic patterns by using a raster scan type cathode ray tube is disclosed. Clock frequencies applied to a parallel-to-serial converter for converting parallel character data to serial data and a parallel-to-serial converter for converting parallel graphic data to serial data are different from each other so that the number of dots displayed on the cathode ray tube in one-character display period for the character data is different from that for the graphic data.

Claims

1. A display device comprising:

display memories for storing character codes and graphic images corresponding to characters and graphs to be displayed in superposed relation on a screen of a raster-scan type cathode ray tube;

first and second parallel-to-serial converters for reading out plural-bit parallel graphic data and plural-bit parallel character data from said display memories in synchronism with a raster-scan timing of said tube in order to output graphic serial data and character serial data respectively;

logic means for logically combining the output graphic serial data and character serial data to produce a video signal to be applied to said cathode ray tube;

a fixed oscillator for generating and applying a first parallel-to-serial conversion control clock signal to said first parallel-to-serial converter;

a PLL circuit for generating and applying a second parallel-to-serial conversion control clock signal to said second parallel-to-serial converter;

means for generating first and second data load signals to cause respective data read-out operations of said first and second converters and for synchronizing said PLL circuit by comparing generated first and second data load signals to selectively produce any of a plurality of numbers of displayed character dots which may be different from a number of displayed graphic dots, whereby the character font of displayed characters can be freely changed irrespective to graphic dots.

2. A display device comprising:

display memories for storing character codes and graphic images corresponding to characters and graphs to be displayed in superposed relation on a screen of a raster-scan type cathode ray tube;

first and second parallel-to-serial converters for reading out plural-bit parallel graphic data and plural-bit parallel character data from said display memories in synchronism with a raster-scan timing of said tube in order to output graphic serial data and character serial data respectively;

logic means for logically combining the output graphic serial data and character serial data to produce a video signal to be applied to said cathode ray tube;

a PLL circuit for generating and applying a first parallel-to-serial conversion control clock signal to said first parallel-to-serial converter;

a fixed oscillator for generating and applying a second parallel-to-serial conversion control clock signal to said second parallel-to-serial converter;

means for generating first and second data load signals to cause respective data read-out operations of said first and second converters and for synchronizing said PLL circuit by comparing generated first and second data load signals to selectively produce any of a plurality of numbers of displayed graphic dots which may be different from a number of displayed character dots, whereby the graphic font of displayed graph images can be freely changed irrespective of character dots.