Virtual ground read-only-memory for electronic calculator or dig

Details Virtual ground read-only-memory for electronic calculator or dig Virtual ground read-only-memory for electronic calculator or dig

1974-11-19

1977-05-03

Malzahn, David H.

Communications: electrical

Digital comparator systems

340173SP, G11C 1700

Patent

active

040217817

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 space on the chip by employing a virtual ground feature and to operate fast due to 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 and to an output line, using a minimum number of transistors. The Y lines are precharged to a value significantly less than the chip supply voltage, so that operating speed is enhanced.

REFERENCES:
patent: 3721964 (1973-03-01), Burrett et al.
patent: 3728696 (1973-04-01), Polkinghorn
patent: 3742592 (1973-07-01), Rizzi et al.
patent: 3892957 (1975-07-01), Bryant

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