GB1117809A - Control system for a display device - Google Patents

Abstract

1,117,809. Cathode-ray tube displays. INTERNATIONAL BUSINESS MACHINES CORPORATION. 28 Oct., 1966 [1 Nov., 1965], No. 48335/66. Heading H4T. In an arrangement in which characters are traced on the screen of a cathode-ray display tube by deflecting the beam between coordinate address points in a matrix, signals determining each character are translated into a plurality of sets of coded signals each set of which determines address points in a respective different size of matrix, all matrices being symmetrical about a common centre position. The invention is described in connection with a system in which a main deflection yoke 14, 16 (Fig. 1) is utilized to trace curves such as 150, 152, (Fig. 4) whilst an auxiliary deflection yoke 18, 20 is utilized to display, on such curves, symbols such as 158, 160, 162, 164, 166, it being required that the symbols, particularly when they indicate the positions of data from which the curves are drawn, be centred on the curve and that this location remain fixed if the symbols are changed in size as indicated at 168, 170. To this end the central processor unit or computer 10, which supplies signals controlling the curve tracing to digital-to-analog (D/A) converters 30, 32 and signals determining the character symbols to a character generator 42, also provides a beam blanking control signal on line 60, signals comprising a two-bit binary code indicative of three different sizes of characters on lines 70, 72 and a signal CM indicative of the non-character tracing mode on line 68. The latter signals are fed to translators 44, 46 (detailed in Fig. 2, not shown) which, during the non-character tracing mode (i.e. during the tracing of curves by yoke 14, 16), supply yoke 18, 20 via D/A converters 34, 36 with a " Home Position " signal specified by a 32 bit binary code and defining a common centre point for each of three different sizes of matrices A, B, C (Fig. 3). In the character tracing mode the matrix origins OA, OB, OC are then specified with respect to this centre point from which the character symbols are traced under the control of a three bit binary code from the character generator 42 which is converted by the translators to a code appropriate to the particular matrix.