Combinatorial Logic

Implement truth table

• Library:

• Simulink / Logic and Bit Operations

• 

Description

The Combinatorial Logic block implements a standard truth table for modeling programmable logic arrays (PLAs), logic circuits, decision tables, and other Boolean expressions. You can use this block in conjunction with Memory blocks to implement finite-state machines or flip-flops.

Ports

Input

Port_1 — Input signal

vector

Input signal, specified as a vector. The type of signals accepted by a Combinatorial Logic block depends on whether you selected the Boolean logic signals option (see Implement logic signals as Boolean data (vs. double)). If this option is enabled, the block accepts real signals of type Boolean or double.

Data Types: double | Boolean

Output

Port_2 — Output signal

scalar | vector

Output signal, double if the truth table contains non-Boolean values of type double; Boolean otherwise. The type of the output is the same as that of the input except that the block outputs double if the input is Boolean and the truth table contains non-Boolean values.

Data Types: double | Boolean

Parameters

Truth table — Matrix of outputs

matrix

You specify a matrix that defines all possible block outputs as the Truth table parameter. Each row of the matrix contains the output for a different combination of input elements. You must specify outputs for every combination of inputs. The number of columns is the number of block outputs.

The Truth table parameter can have Boolean values (0 or 1) of any data type, including fixed-point data types. If the table contains non-Boolean values, the data type of the table must be double.

The relationship between the number of inputs and the number of rows is:

number of rows = 2(number of inputs)

Simulink^® returns a row of the matrix by computing the row's index from the input vector elements. Simulink computes the index by building a binary number where input vector elements having zero values are 0 and elements having nonzero values are 1, then adding 1 to the result. For an input vector, u, of m elements:

row index = 1 + u(m)*2⁰ + u(m-1)*2¹ + ... + u(1)*2^m-1

Programmatic Use

Block Parameter: TruthTable

Type: character vector

Values: matrix

Default: '[0 0;0 1;0 1;1 0;0 1;1 0;1 0;1 1]'

Model Examples

Two-Input AND Logic

Builds a two-input AND function, which returns 1 when both input elements are 1, and 0 otherwise.

Open Model

Circuit Logic

This sample circuit has three inputs: the two bits ( a and b) to be summed and a carry-in bit (c). It has two outputs: the carry-out bit (c') and the sum bit (s).

Open Model

Building a Clutch Lock-Up Model

Use Simulink® to model and simulate a rotating clutch system. Although modeling a clutch system is difficult because of topological changes in the system dynamics during lockup, this example shows how Simulink's enabled subsystems easily handle such problems. We illustrate how to employ important Simulink modeling concepts in the creation of the clutch simulation. Designers can apply these concepts to many models with strong discontinuities and constraints that may change dynamically.

Open Model

Power Window Control Project

Use MathWorks® software and the Model-Based Development process to go from concept to implementation for a power window system for an automobile. This example uses Simulink®, Simulink® Coverage™, DSP System Toolbox™, Simscape™ Multibody™, Fixed-Point Designer™, Simscape™ Electrical™, Simscape™, and Simulink® Real-Time™.

Open Script

Block Characteristics

Data Types	Boolean | double
Direct Feedthrough	yes
Multidimensional Signals	no
Variable-Size Signals	no
Zero-Crossing Detection	no

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced before R2006a