Albuquerque, New Mexico
June 24, 2001
June 24, 2001
June 27, 2001
6.6.1 - 6.6.8
An important aspect of any logic design problem is an easy and direct design method which results in properly documented components; i.e., schematics, expressions, truth tables, etc., which accurately convey the designer’s original thought process. The mixed logic approach, which meets the above requirements, is proposed as a method to be taught in digital design courses. To understand mixed logic, the concepts of positive and negative logic and assertion levels must first be defined. Positive logic is defined as a high voltage level representing a logic 1 and a low voltage level representing a logic 0. Negative logic is the reverse, i.e., a low voltage level represents a logic 1 and a high voltage level represents a logic 0. Assertion levels determine whether a net or signal line in a digital circuit is to be interpreted as positive logic or negative logic. A negative logic assertion level is called active low and is represented by the presence of bubbles on the net in the schematic and a .L suffix on the logic variable. A positive logic assertion level is called active high and is represented by the absence of bubbles on the net in the schematic and a .H suffix on the logic variable. Mixed logic is the use of both positive and negative logic representations in a digital circuit design.
Livingston, D. (2001, June), A Case For Teaching Mixed Logic In Digital Design Paper presented at 2001 Annual Conference, Albuquerque, New Mexico. https://peer.asee.org/8983
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