U. Glaeser

K. Wayne Current
University of California
11.1 Introduction
© 2002 by CRC Press LLC
11
Multiple-Valued Logic
Circuits
11.1 Introduction
11.2 Nonvolatile Multiple-Valued Memory Circuits
Multiple-Valued Read Only Memory • Multiple-Valued
EEPROM and Flash Memory
11.3 Current-Mode CMOS Multiple-Valued
Logic Circuits
CMOS Current Threshold Comparator • Current-Mode
CMOS Binary/Quaternary Encoders and Decoders •
Current-Mode CMOS Quaternary Threshold Logic Full
Adder • Current-Mode CMOS Multiple-Valued
Latch • Current-Mode CMOS Latched Quaternary Logic
Full Adder Circuit • Current-Mode CMOS Algorithmic
Analog-to-Quaternary Converter
11.4 Summary and Conclusion
Multiple-valued logic (MVL) is a hybrid of binary logic and analog signal processing: some of the noise
advantages of a single binary signal are retained, and some of the advantages of a single analog signal’s
ability to provide greater informational content are used. Much work has been done on many of the
theoretical aspects of MVL. The theoretical advantages of MVL in reducing the number of interconnections
required to implement logical functions have been well established and widely acknowledged.
Serious pinout problems encountered in some very large scale integrated (VLSI) circuit designs could
be substantially influenced if signals were allowed to assume four or more states rather than only two.
The same argument applies to the interconnect-limited IC design: if each signal line carries twice as
much information, then only half as many lines are required. Four-valued logic signals easily interface
with the binary world; they may be decoded directly into their two-binary-digit equivalent. Many logical
and arithmetic functions have been shown to be more efficiently implemented with MVL, i.e., fewer
operations, gates, transistors, signal lines, etc., are required. Yet, with all the theoretical advantages, MVL
is not in wide use mainly because MVL circuits cannot provide these advantages without cost. The costs
are typically reduced noise margins, slower raw switching speed due to increased circuit complexity and
functionality, and the burden of proving MVL use improves overall system characteristics. As fabrication
technologies evolve, MVL circuit designers adapt to the new technology-related capabilities and limitations
and create new MVL circuit designs. Many MVL circuits have been proposed that use existing and
proposed silicon and III-V fabrication technologies; that signal with flux, charge, current, voltage, and
photons. A discussion of the extensive range of possible circuit-oriented MVL topics would be very