Design of a Low-cost Character Generator for Remote Computer Displays

Abstract

A requirement exists for a low-cost remote display terminal with alphanumeric and line-drawing capabilities for use with time-shared computer systems. This thesis, conducted as part of the overall remote display design project, was undertaken to investigate novel approaches to character generation, with the goal of drastically reducing present-day costs for such devices. A survey of existing devices and character generation techniques was carried out, and a design approach was chosen which takes advantage of mass-fabrication techniques. This includes using a five-by-seven dot matrix raster and a resistor array "read-only" character memory for the 96 printable symbols of the Revised Proposed ASCII Code. Circuits designed, included a dot matrix generator and a register array memory with selection logic sense amplifiers, and a shift register output buffer. An experimental character generator with an eight-word memory was built, largely using integrated circuits and was found to work as desired. It is concluded that the design approach will yield a character generator that is of low enough cost to find wide use in remote computer terminals.