| 摘要 |
A three state logic input recognizes three logic levels: an intermediate level in addition to the conventional "high" and "low" levels employed by binary logic systems. The three state device may be used in purely ternary logic systems or in "hybrid" systems which combine binary and ternary logic. In a preferred embodiment, the new three state logic device comprises a "passive driver" which is connected to produce one of three predetermined logic levels in corresponding to impedance paths from its input terminal through an external circuit to a positive or negative voltage supply. In hybrid ternary/binary applications, the new three state input device includes a decoder that is connected to decode the three predetermined logic levels provided by the passive driver into binary logic for use by associated binary logic devices. In a digital to analog converter application, the three state input device is employed to recognize both a binary logic and a control signal at one input pin to the DAC.
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