Apparatus and method for displaying characters in a bit mapped graphics system

An apparatus for supplying character bit maps and graphics patterns to a visible display memory, said character information memory including an address table and pairs of macro-instructions and character bit maps, wherein each of said pairs corresponds to one character of a character set, wherein each of said macro-instructions includes a character address that points to the memory location of its corresponding bit map, and wherein said address table includes macro-instruction addresses that point to the memory locations of said macro-instructions, said apparatus comprising:

• processing means coupled to said character information memory and said visible display memory for operating in a macro mode for supplying character bit maps to said visible display memory and for operating in a graphics mode for supplying graphics patterns to said visible display memory;
• said processing means is operable in said macro mode for receiving a character code that designates an action to be executed, for fetching a macro-instruction corresponding to said character code from said character information memory, and means, including an arithmetic logic unit means, for executing said macro-instructions to selectively combine logically or arithmetically said character from said character information memory with said designated portion of said contents of said visible display memory and copy the result therefrom back into said visible display memory;
• and
• said processing means is operable in said graphics mode for receiving graphics instructions from said central processing unit, and for executing said graphics instructions to place graphics patterns into said visible display memory.

An apparatus for supplying character descriptive information and graphics patterns to a bit mapped display memory, said apparatus comprising:

• memory means for storing character descriptive information for a character set, said memory means including an address table and pairs of macro-instructions and character bit maps, wherein each of said pairs corresponds to one character of said character set, wherein each of said macro-instructions includes a character address that points to the memory location of its corresponding character bit map, and wherein said address table includes macro-instruction addresses that point to the memory locations of said macro-instructions;
• and
• processing means, coupled to said memory means, for operating in a macro mode for supplying character descriptive information to said bit mapped display memory and for operating in a graphics mode for supplying graphics patterns to said bit mapped display memory;
• said processing means is operable in said macro mode for receiving a character code that designates a character to be supplied, for fetching a macro-instruction corresponding to said character code from said memory means, and means, including an arithmetic logic unit means, for executing said macro-instructions to selectively combine logically or arithmetically said character from said character information memory with said designated portion of said contents of said visible display memory and copy the result therefrom back into said visible display memory;
• said processing means is operable in said graphics mode for receiving graphics instructions from said central processing unit, and for executing said graphics instructions to place graphics patterns into said bit mapped display memory.

A method of supplying character descriptive information to a visible portion of a bit mapped display memory, said method comprising the steps of:

• providing a character information memory that includes character descriptive information for all characters of a character set, said character information memory including an address table and pairs of macro-instructions and character bit maps, wherein each of said pairs corresponds to one character of said character set, wherein each of said macro-instructions includes a character address that points to the memory location of its corresponding character bit map, and wherein said addresss table includes macro-instruction addresses that point to the memory locations of said macro-instructions;
• receiving a character code that identifies a character to be displayed;
• fetching a macro-instruction corresponding to said character code from said character information memory;
• and
• executing in an arithmetic logic unit said macro-instructions to selectively combine logically or arithmetically said character from said character information memory with said designated portion of said contents of said visible display memory and copy the result therefrom back into said visible display memory.

An apparatus for displaying characters and graphics patterns on a display, said apparatus comprising:

• a central processing unit for supplying character codes and graphics instructions;
• a pixel data manager circuit, coupled to said central processing unit to receive said character codes and graphics instructions, said pixel data manager circuit is operable for defining a bit map representation of characters and graphics patterns;
• a character information memory, coupled to said pixel data manager circuit, for storing and supplying character descriptive information, said character information memory including an address table, macro-instructions, and character bit maps;
• a visible display memory, coupled to said pixel data manager circuit, for storing a bit map representation of characters and graphics patterns to be displayed;
• a display driver circuit, coupled to said visible display memory, for scanning said visible display memory and for generating a display signal in response thereto;
• and
• a display device, coupled to said display driver circuit, for receiving said display signal and for displaying an image in response thereto;
• said pixel data manager circuit is operable for supplying bit map representatives of graphics patterns to said visible display memory by executing said graphics instructions, said pixel data manager circuit is also operable for supplying bit map representations of characters to said visible display memory by fetching a corresponding macro-instruction from said character information memory, and means, including an arithmetic logic unit means, for executing said macro-instructions to selectively combine logically or arithmetically said character from said character information memory with said designated portion of said contents of said visible display memory and copy the result therefrom back into said visible display memory.