Apparatus for generating signals for producing a display of characters

摘要

Apparatus for rounding of a character produced as a character segment matrix pattern for display on a raster scanned display in which a read-only memory storing the character segment matrix patterns for the characters to be displayed is arranged to produce the entire matrix pattern for a selected character in parallel at any one time. A parallel gating means selects from the matrix pattern a selected row of the matrix and also the immediately preceding row or the immediately following row depending upon which is required at the time for character rounding. The bits of the selected row are applied in parallel to a first shifting register and the bits of both rows produced by the gating means are applied in parallel to a character rounding logic circuit which is arranged to detect the presence of diagonal lines in the character and produce the appropriate rounding elements. The rounding elements are applied in parallel to a second shifting register and the two shifting registers are read out in timed relationship to one another so that their outputs can be combined to produce a video signal representing a rounded character. The parallel gating means receives in addition to a character row address a further input which determines whether it is the immediately preceding or the immediately following row which produces the second output. The signal applied to the further input indicates whether the field of the raster being scanned consists of odd or even lines, or in the case of a double height character it consists of the least significant bit of the character row address.