Patent US 4,243,987

A display processor is disclosed that receives digitally encoded text data and generates video data signals to produce video images of dot matrix alphanumeric characters on a cathode ray tube display in a format that emulates a full page of typewritten copy. The display processor receives ASCII coded character data and digitally encoded text manipulative data and generates horizontal sync, vertical sync and video data in the form of a display scan line dot pattern. The display processor includes a display refresh memory for storing coded text and manipulative data, a character generator including a font memory and video output circuitry. Operation of the display processor is under a set of microcoded instructions outputted from an internal instruction generator in a repeating program sequence, with a random access memory being utilized to store refresh memory read and write addresses and other data required during execution of the program sequence. Scan line dot patterns outputted from the font memory in parallel are converted into serial data in the video output circuitry by ping-ponging two serial shift registers.