Apparatus for generating graphic coordinates for scan type graphic display

A coordinate conversion device suitable for use with a scan type display having a plurality of scan lines, each scan line having a plurality of pixels, said coordinate conversion device comprising:

• a horizontal position transformation circuit responsive to a screen starting point of each scan line for generating a horizontal graphics position on a per pixel basis;
• and
• a vertical position transformation circuit responsive to said screen starting points for generating a vertical graphics position on a per pixel basis;
• said horizontal position transformation circuit comprising:
• a horizontal start position generator for generating a respective graphics horizontal start position corresponding to said starting points;
• a horizontal step value generator for generating a graphics horizontal step value associated with each scan line;
• a first adder having an output for adding, on a per pixel basis, said horizontal step value and said horizontal graphics position;
• a horizontal position register responsive to said graphics horizontal start position and said output of said first adder for generating said horizontal graphics position;
• and
• said vertical position transformation circuit comprising:
• a vertical start position generator for generating a respective graphics vertical start position corresponding to said starting points;
• a vertical step value generator for generating a graphics vertical step value associated with each scan line;
• a second adder having an output for adding, on a per pixel basis, said vertical step value and said vertical graphics position;
• and
• a vertical position register responsive to said graphics vertical start position and said output of said second adder for generating said vertical graphics position;
• said horizontal start position generator including:
• a first horizontal position generator responsive to said starting points for generating a respective first horizontal parameter according to an automatic horizontal accumulation step value;
• a second horizontal position generator responsive to said starting points for generating a respective second horizontal parameter according to a horizontal offset from a first memory;
• a first multiplexer for selecting, on a screen display basis according to a first horizontal selection control signal, one of said first and said second horizontal parameters to generate said graphics horizontal start position;
• said vertical start position generator including:
• a first vertical position generator for generating a first vertical parameter according to an automatic vertical accumulation step value;
• a second vertical position generator for generating a second vertical parameter according to a vertical offset from a second memory;
• and
• a second multiplexer for selecting, on a screen display basis according to a first vertical selection control signal, one of said first and said second vertical parameters to generate said graphics vertical start position.