Display control apparatus of scanning type display

A display control apparatus of a scanning type display for displaying an image on a screen through repetition of a horizontal scanning operation and a vertical scanning operation,

• said scanning type display comprising an arrangement of a relatively large plurality (m.times.n) of dots on the screen arranged in the horizontal and vertical directions by the numbers m and n, respectively, an image symbol as a unit being displayed comprising an arrangement of a relatively small plurality (x.times.y) of dots arranged in the horizontal and vertical directions by the dot numbers x and y, respectively, one or more of image symbols being displayed on the screen arranged in columns of the number (m/x) obtained by dividing the dot number (m) in the horizontal direction of the relatively large plurality (m.times.n) of numbers by the dot number (x) in the horizontal direction of the relatively small plurality (x.times.y) of numbers, said apparatus comprising:
• a character pattern storing memory for storing a plurality of kinds of pattern information concerning characters each being displayed as said unit image symbol and having its own predetermined character identifying information for each kind thereof,
• display control information generating means for generating display control information during one horizontal scanning period,
• said display control information including abscissa information for designating the column in the horizontal direction of said image symbol being displayed on said screen, reference ordinate information of said image symbol, and said character identifying information of said image symbol,
• additional ordinate information generating means for providing additional ordinate information (.DELTA.V) based on a difference between ordinate information preceding by a predetermined number of lines the actual ordinate position of the horizontal scanning line of said scanning type display and ordinate information of said image symbol,
• a first line buffer memory including storing regions for storing at least said character identifying information and said additional ordinate information (.DELTA.V) for each column of said horizontal scanning lines,
• a second line buffer memory including storing regions for storing at least said character identifying information and said additional ordinate information (.DELTA.V) for each column of the horizontal scanning lines spaced apart by a predetermined number of lines from said horizontal scanning lines stored in said first line buffer memory,
• synchronizing signal generating means for generating a synchronizing signal associated with the abscissa and ordinate of the actual scanning position of said horizontal scanning line,
• write/read control means for placing one of said first and second line buffer memories in an information write mode and for placing the other of said first and second line buffer memories in an information read mode alternately at every predetermined number of lines of said horizontal scanning lines, and
• pattern information withdrawal control means responsive to the read output from said other line buffer memory for reading the pattern information of the kind corresponding to the character identifying information from said character pattern storing memory for providing the same to said scanning type display.