E (verification language)

e is a hardware verification language (HVL) which is tailored to implementing highly flexible and reusable verification testbenches.

e was first developed in 1992 in Israel by Yoav Hollander for his Specman software. In 1995 he founded a company, InSpec (later renamed Verisity), to commercialize the software. The product was introduced at the 1996 Design Automation Conference. Verisity has since been acquired by Cadence Design Systems.

Main features of e are:

The e language uses an aspect-oriented programming (AOP) approach, which is an extension of the object-oriented programming approach to specifically address the needs required in functional verification. AOP is a key feature in that it allows for users to easily bolt on additional functionality to existing code in a non-invasive manner. This permits easy reuse and code maintenance which is a huge benefit in the hardware world, where designs are continually being tweaked to meet market demands throughout the project lifecycle. AOP also addresses cross cutting concerns (features that cut across various sections of the code) easily by allowing users to extend either specific or all instances of a particular struct to add functionality. Users can extend several structs to add functionality related to a particular feature and bundle the extensions into a single file if desired, providing for more organized file partitioning.

Executable e code is enclosed within code-segment markers <' and '>:

e also has two kinds of classes:

A class may contain fields, methods, ports and constraints. Fields can be of type integer, real, enum, string and even complex objects. The code segment shows a unit called 'environment_u' being instantiated within the e root 'sys'. This environment_u class contains a list of 5 packet_s objects and this packet_s class contains two fields and a method.

In e each field is randomized by default. Field randomization can be controlled by hard constraints, soft constraints or even be turned off completely. Soft constraints are used as the default constraints, and may be automatically overridden by the test layer if a conflict occurs. Otherwise it behaves like a regular constraint.

e supports assertions with temporal expressions. A temporal expression is used at the same syntactic level as fields and methods and is thereby declarative by nature. A temporal expression describes timed behavior.