JPS54120537A - Line texture generating circuit of display unit - Google Patents

Abstract

PURPOSE:To perform definitely the end process of a line by providing a comparing method which generates its output when the sum of the variations of X and Y axis coordinate values becomes close to the sum of X and Y axis increments within a fixed value. CONSTITUTION:If each line-pattern intermittent signal is so stored in ROM9 that the memory contents of the head address of ROM 9 of texture generating circuit 6 and several bits following it will be ''0'' equivalent to the mark part of a line, data of the circumference of starting point (X1, Y1) of line data are not inhibited from being written and the starting-point part is displayed definitely. Next, comparator circuit 15 sends out an output signal, when a difference between output discrete value Cn 12 inscreasing according to the output of line data and output value DELTAX+DELTAY of adder 14 (X and Y axis increments stored in X and Y registers 8a and 8b of DDA circuit 2) becomes below a fixed value, to allow gate 11 to close, and afterwards, line data till the end point are written in picture memory 4. Therefore, the end-point part of the line has no space and the terminal of the line will be extracted definitely in terms of display.