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 Logic circuit

Details
Inventors: Furihata, Makoto; Ogura, Setsuo; Kondo, Shizuo; Minamimura, Eiji;
Assignee: Hitachi, Ltd. (Tokyo, JP)
Primary Examiner: Popek; Joseph A.
Assistant Examiner:
Attorney, Agent or Firm: Antonelli, Terry & Wands

A logic circuit of a large scale which consumes small amounts of electric power is comprised of a plurality of ROM portions each formed of IIL circuits. Input signal lines are commonly used to transmit input signals to the ROM portions. The plurality of ROM portions are selectively operated by ROM select signals, and outputs corresponding to the input signals are obtained from a selected ROM portion. To select a particular ROM portion out of the plurality of ROM portions, the emitters of inverse npn transistors of IIL circuits constituting the selected ROM portion are rendered to assume ground potential. In the meantime, the emitters of the inverse npn transistors of IIL circuits in the non-selected ROM portions are held in a floating condition. This makes it possible to obtain a logic circuit which consumes small amounts of electric power with a very simple construction since the non-selected ROM portions consume no power.

DETAILED DESCRIPTION The invention will be described below briefly.
Namely, a plurality of ROM's of a large capacity constituted by IIL circuits are prepared, and one of them is selected by the high-order bits of an input signal.
Further, the input and output terminals of the ROM's are commonly formed.
A ROM can be selected very simply by rendering the emitters of inverse transistors constituting the IIL circuits of the selected ROM to assume ground potential while the emitters of inverse transistors constituting the IIL circuits of non-selected ROM's are held in a floating condition, relying upon switching means.
The above-mentioned structure makes it possible to accomplish the object of the present invention, i.
e.
, to obtain logic circuits constituted by IIL circuits or digital memory circuits such as large ROM's , without so increasing the consumption of electric power and without extremely increasing the capacity of drive buffer.


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