Display monitor for computer numerical control systems

Claim 1

A display for alphanumeric characters comprising a cathode ray tube having a screen with luminescent dots in a rectangular array whereby a character display is produced by brightening selected dots in plural character columns and rows, a dot clock for generating a train of dot clock pulses at a predetermined frequency, means connected with the clock means and with the cathode ray tube for causing the cathode ray to scan the screen in a predetermined raster in timed relation with said clock pulses, dot signal means for producing a dot signal which has a pulse or a space corresponding to each clock pulse, intensity control means connected with the cathode ray tube and the dot signal means for brightening the trace of the ray on the screen in response to a pulse and for darkening it in response to a space, a memory for storing character codes representing a plurality of characters which are to be displayed at predetermined locations on said screen, a character generator for sequentially producing plural binary signals each representing a row of dots of a character to be displayed, a shift register connected between the character generator and the dot signal means, a buffer connected between said memory and said character generator, an address generator including a first frequency divider having its input connected with the dot clock for counting character columns, a line position address counter having a counter output and a divider output, a character line counter having a counter output and a divider output, and a frame position address counter having a counter output, all of said dividers and counters being connected in cascade in the order named with respect to their inputs and divider outputs, the counter output of the line position address counter and the counter output of the frame position address counter being connected with said memory for advancing the output of the memory from one character code to the next, the counter output of said character line counter being connected with said character generator for advancing the output thereof from one dot line to the next, the output of said first divider being connected with said buffer for transferring one character at a time from the memory to said character generator, the input of said first divider being connected with said shift register for serially applying the output of the character generator to the input of said dot signal means, whereby a character of a certain normal size is produced on said screen, a second frequency divider selectably connectable between said dot clock and the input of said first divider and a third frequency divider selectably connectable between the divider output of said line position address counter and the input of said character line counter, switching means for simultaneously actuating said second and third dividers whereby a character of magnified size is produced on said screen.