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US 5,200,907 AGranted
Transmission gate logic design method
OwnerDzung J. Traninventor
Life of this patent
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Abstract
A method of designing a logic circuit for implementing a predetermined boolean function defines a binary tree structure formed of transmission gate multiplexer (TGM) circuits. The TGM tree structure includes one binary stage for each input variable. A resulting logic circuit design is reduced by one or more stages to improve performance by employing selected boolean functions of the most significant bits of the input variables as input signals to a reduced tree structure. The method is applicable circuit design in all MOS-type technologies including NMOS, PMOS, CMOS, BiMOS, FET and the like.
Claims16
A method of constructing a transmission gate logic circuit for providing a predetermined boolean function of N input variables, comprising:
- providing an N-stage transmission gate multiplexer (TGM) binary tree structure formed of TGM circuits and including a first stage and an Nth final stage, each TGM circuit having first and second input terminals, first and second control terminals and an output terminal;
- coupling each input variable and its complement, respectively, to the first and second control terminals of a respective stage of the tree structure, seriatim, the most significant input variable (msb) being coupled to the Nth stage of the tree structure, and the least significant input variable (lsb) being coupled to the first stage;
- identifying a series of 2.sup.N paths through the three structure, from the final stage input terminals to the first stage output terminal, each path having a corresponding input terminal in the final stage, so that each path corresponds to a unique binary state of the input variables;
- designating as a TRUE path each one of the series of paths for which the predetermined boolean function is true;
- designating as a FALSE path each one of the series of paths for which the predetermined boolean function is false;
- for each TRUE path, coupling a logical true signal to the corresponding input terminal;
- and
- for each FALSE path, coupling a logical false signal to the corresponding input terminal;
- whereby, in operation of the logic circuit, the logic states of the input variables control the TGM circuits to route a logic signal to the output terminal in accordance with the predetermined boolean function.
6 more elements
A method of constructing a transmission gate logic circuit to provide a predetermined boolean function of N input variables, the circuit including a K-stage transmission gate multiplexer (TGM) tree structure, where K is less than N by an integer number M, comprising:
- assigning to each input variable a respective binary weight, so that the N input variables define a series of bits (MSB :
- MSB-1:
- MSB-2. . . LSB) in order of binary significance;
- defining an K-stage TGM tree structure formed of TGM circuits and including a first stage and a final stage, each stage having first and second control terminals and the final stage including a series of input terminals;
- coupling each of the K least significant input variables and their complements, respectively, to the first and second control terminals of respective stages of the tree structure in order of binary significance, the least significant input variable being coupled to control the first stage, so that each final stage input terminal corresponds to a unique state of the K least significant input variables;
- for each state of the K least significant input variables, expressing the predetermined boolean function as a corresponding function of the M most significant input variables;
- and
- for each possible state of the K least significant input variables, coupling the corresponding final stage input terminal to receive a respective logic signal defined by the corresponding function of the M most significant input variables.
5 more elements
A method of constructing a transmission gate logic circuit for providing a predetermined boolean function of N input variables, comprising:
- defining an N-stage transmission gate multiplexer (TGM) binary tree structure having 2.sup.N input terminals and an output terminal, each stage of the tree structure having a corresponding control input terminal;
- coupling each input variable to a corresponding one of the control input terminals according to binary significance, the most significant input variable (msb) being coupled to the Nth stage of the tree structure, and the least significant input variable (lsb) being coupled to the first stage;
- identifying a series of 2.sup.N paths through the tree structure, each path extending from a respective one of the input terminals to the output terminal, so that each path corresponds to a unique state of the input variables;
- designating as a TRUE path each one of the series of paths for which the predetermined boolean function is true for the corresponding state of the input variables;
- designating as a FALSE path each one of the series of paths for which the predetermined boolean function is false for the corresponding state of the input variables;
- for each TRUE path, coupling a logical true signal to the corresponding input terminal;
- and
- for each FALSE path, coupling a logical false signal to the corresponding input terminal.
5 more elements
A method of constructing a transmission gate logic circuit for providing a predetermined boolean function of N input variables, comprising:
- defining an N-stage transmission gate multiplexer (TGM) binary tree structure having 2.sup.N input terminals and an output terminal, each stage of the tree structure having a corresponding control input terminal;
- coupling each input variable to a corresponding one of the control input terminals in order of binary significance, the most significant input variable (msb) being coupled to the Nth stage of the tree structure, and the least significant input variable (lsb) being coupled to the first stage;
- identifying a series of 2.sup.N paths through the tree structure, each path extending from a respective one of the input terminals to the output terminal, so that each path corresponds to a unique state of the input variables;
- in each path for which the predetermined boolean function is true for the corresponding state of the input variables, coupling a logical true signal to the corresponding input terminal;
- and
- in each path for which the predetermined boolean function is false for the corresponding state of the input variables;
- coupling a logical false signal to the corresponding input terminal.
4 more elements
A method of constructing a transmission gate logic circuit for providing a predetermined boolean function of more than two binary input variables, the method comprising:
- providing a plurality of transmission gate multiplexers interconnected so as to form a TGM binary tree structure including a first stage and a second stage, each stage having a pair of complementary control terminals and each TGM including a pair of input terminals and an output terminal, the first stage TGM output terminal defining a Z output terminal;
- coupling a first one of the input variables (lsb) and its complement signal to the respective first stage control terminals;
- coupling a second one of the input variables (lsb+1) and its complement to the respective second stage control terminals;
- and
- for each second stage TGM input terminal, selecting a corresponding binary input signal from a group of input signals that includes at least two different input signals selected from among a logic HIGH, a logic LOW, a third one of the input variables and the complement of the third one of the input variables in accordance with the predetermined boolean function;
- and
- coupling each second stage TGM input terminal to receive the corresponding selected input signal.
4 more elements
Dependencies are inferred from the claim text.