Abstract: An electronic calculator system of the type having a keyboard input and a visual display readout is implemented in MOS/LSI semiconductor chips having a data memory, an arithmetic unit, a read-only-memory for storing instruction words, and control circuitry for operating the system in response to keyboard inputs, all in monolithic semiconductor units. The keyboard and display are scanned by timing signals generated in the semiconductor unit by a register associated with the data memory.

Abstract: A read-only-memory for use in an electronic calculator or the like, implemented in a large-scale-integrated MOS semiconductor chip. The ROM is designed to save area on the chip by employing a virtual ground feature and conserve power by a precharge system. The memory cells are in an array defining X and Y lines, with the presence or absence of a bit being determined by thin oxide under an X line between adjacent Y lines. Ground lines are provided for groups of Y lines, and the Y-decode matrix includes an arrangement for connecting a selected Y-line to a non-adjacent ground line. Only the X decode section is precharged rather than all the X lines. The entire decode and read out is accomplished in a small part of the instruction cycle of the calculator.