Constant writing rate digital stroke character generator having minimal data storage requirements

• US 3,952,297 A
• Filed: 08/01/1974
• Issued: 04/20/1976
• Est. Priority Date: 08/01/1974
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Smith, Phillip R., Stauffer, Franklin K.
• Primary Examiner(s): Curtis, Marshall M.
• Application Number:
  US05/493,451
• Time in Patent Office: 628 Days
• Field of Search: 340/324 A, 340/324 AD, 340/325, 340/379, 235/198
• US Class Current: 345/18
• CPC Class Codes: G09G 1/10 the deflection signals being produced by essentially digital means, e.g. incrementally

Abstract

A digital character generator with minimal storage requirements for use in random access display systems. Each character or symbol is made up of patterns of straight line segments called macro-strokes. Each macro-stroke in turn is made up of a predetermined number of connected portions or micro-strokes lying in a straight line. Each micro-stroke is of substantially the same length independent of the number of micro-strokes in a macro-stroke and of the directional orientation of the macrostroke. To store a character or symbol each macro-stroke is divided into its micro-strokes and the micro-strokes resolved into X and Y components. The X and Y components are stored along with the number of micro-strokes in the particular macro-stroke. Along with this information is stored the address and memory of the next macro-stroke within the character or symbol. The X and Y components of the micro-strokes are continuously accumulated until the end of the macro-stroke is reached as determined by the number of micro-strokes within the macro-stroke. The memory is then sequenced to the next address to begin the generation of the next macro-stroke.

Claims

1. In combination:

means for storing data representing portions of straight line segments of characters to be displayed, said data comprising the magnitude and direction of each of said portions for at least two axes;

means for periodically accumulating said data at a constant rate for producing said straight line segments of said characters;

means for storing a digital number representing the number of said portions in each of said segments;

counting means operating in response to said number; and

means for displaying said characters.

2. The combination of claim 1 wherein said means for storing said data and said means for storing said number comprise a read-only-memory.

3. The combination of claim 2 wherein said accumulating means comprises in combination:

digital adder means; and

digital storage register means, inputs of said register means being coupled to outputs of said adder means and outputs of said register means being coupled to inputs of said adder means, other inputs of said adder means being coupled to means for supplying said digital data.

4. The combination of claim 3 further comprising means for addressing said means for storing said data and said means for storing said number.

5. The combination of claim 4 wherein said addressing means comprises a binary counter, outputs of said counter being coupled to address inputs of said storing means.

6. The combination of claim 5 further comprising means for presetting said counting means to a predetermined count.

7. A character generator for producing signals for deflecting the beam of a cathode-ray tube in predetermined character patterns, the character patterns being divided into straight line segments and said straight line segments each being divided into a predetermined number of portions, said character generator comprising in combination:

a memory, said memory storing data representing the magnitude and direction of said portions and the number of said portions in each straight line segment;

a plurality of registers for receiving said data from said memory and for storing said data;

first counter means, said first counter means operating in response to said number;

means for repetitively adding said data to a present stored position; and

means for addressing said memory.

8. The combination of claim 7 wherein said portions are resolved into X and Y components and wherein one of said registers is provided for said X components and another of said registers is provided for Y components.

9. The combination of claim 8 wherein said memory comprises a read-only-memory.

10. The combination of claim 9 wherein said counter is operated one or more times for each addition performed by said repetitively adding means.

11. The combination of claim 9 wherein said memory further stores addresses in said memory corresponding to successive segments of said characters.

12. The combination of claim 11 wherein said addressing means further comprises:

second counter means;

means for presetting said second counter means, said presetting means presetting said counter with an externally supplied character code prior to the generation of the first straight line segment of each character and with said addresses from said memory for succeeding straight line segments of said character.

13. The combination of claim 9 wherein said memory further stores a plurality of unblanking bits, one of said unblanking bits being stored for each of said straight-line segments.

14. The combination of claim 9 wherein each of said portions among all straight-line segments within each of said characters is of substantially the same length.

15. A character generator for producing signals for deflecting the beam of a cathode-ray tube in predetermined character patterns, said character patterns each being divided into straight line segments, each of said straight line segments being divided into a predetermined number of connected straight line portions, said character generator comprising in combination:

a memory, a data word being stored in said memory for each of said segments in each of said character patterns, each of said data words comprising data representing the magnitude and direction of said straight line portions for each of two axes for the segment to which said data word corresponds, the number of said portions in said segment, and an address in said memory of the word corresponding to the next one of said segments;

a first counter for addressing said memory, said counter being preset prior to the display of the first one of said segments in each of said characters by a code corresponding to said character and preset for each succeeding segment in said character by said address within said data word;

a second counter for counting said number of said portions in each of said segments, said second counter being incremented one count for each of said segments, and said first counter being incremented in response to one or more outputs of said second counter; and

two accumulators, said data representing said magnitude and direction of said straight line portions being coupled from said memory to said accumulators, one of said accumulators being provided for each of said axes.

16. The combination of claim 15 further comprising:

switching means for coupling one of said code and said address from within said data word to inputs of said first counter for presetting said first counter.

17. The combination of claim 16 further comprising:

two registers, inputs of said registers being coupled to said memory and outputs of said registers being coupled to said accumulators.

18. The combination of claim 16 further comprising:

two analog-to-digital converters, inputs of said converters being coupled to outputs of said accumulators.

19. The combination of claim 16 wherein each of said data words further comprises:

one or more binary bits for controlling video intensity upon display means of the segment to which said data word corresponds.

20. The combination of claim 19 wherein said binary bits are one in number.

21. The combination of claim 19 further comprising:

cathode-ray tube display means.

22. The combination of claim 15 wherein some of said data words are used in the generation of a plurality of said characters.