The formal methods are techniques making it possible to ensure the good comprehension of the awaited functions of a system. These functions being able to be temporal, deterministic,…

They make it possible moreover to facilitate the interconnection of functional modules of different origins (software, material) while being based on common mathematical representations.

Historic insight

The concepts related to these methods of analysis were developed in the years 1980 for the data-processing coding.

In the years 1990, these concepts were extended to the design of the numerical electronic circuits. To date, it is not possible to extend these techniques to the entirety of the analogical circuits. This limit is intrinsic with the approach of the discrete deterministic systems.

Categories of tools

The whole of the tools dedicated to the electronic circuits being based on formal methods is divided into two big families: the model checking or the equivalent checking (one finds also methods checking equivalence between models for the programs data processing as well as approaches by components).

Model Checking

The tools of this type use only one representation of the system.

From there, several approaches are possible to check the answer of the system, its determinism, and thus its adequacy with its definition.

Here a nonexhaustive list of these techniques which base all on the presence of a suitable specification of awaited functional of the system:

1. Theorem Prooving : the system is defined in the form of a mathematical theorem.

2. Property Checking : the system is cut out in the form of simple unit properties. The sum of these properties having to define the whole of the valid states of the system.
3. Static Analysis : This technique common to data processing can be connected with the property checking , but it has the defect not to be able to check dynamic behaviors of the system.
4. Symbolic Model Cheking

Checking equivalent

The tools of this type are based on the fact that the design of a electronic circuit implies several models, each one having its own constraints, and the fact that the complexity of those made that often the unit consists in integrating building blocks of various origins:

1. functional Description (Behavioral)
2. Description of the transfers between registers (RTL)
3. Description in the form of a network of electric switches (netlist)
4. space Allowance of the network of switches on the component (P&R, Layout)

The tools of this type thus compare the model in progress with a model, known as of reference (Model Golden delicious), which was checked as correspondent with unit waitings, or of interface.

There is comparison between two of the same models level (behavioral vs. behavioral, RTL vs. RTL, netlist vs. netlist), or of successive levels (behavioral vs. RTL, behavioral vs. netlist, RTL vs. netlist).

N.B.: Currently, the tools behavioral vs. xxx are not functional

Notes and references of the article

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