Command and Data Instruction Level

Concept

An intermediate level of abstraction used in stimuli generation for hardware design verification, in which stimulus items are expressed as groups of commands and data instructions. It sits between the higher-level Sequence Level and the lower-level Bit Level in the abstraction hierarchy of a test generator.

First seen 7/12/2026

Last seen 7/12/2026

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Overview

The Command and Data Instruction Level is a level of abstraction used in stimulus (test) generation for hardware design verification. In this level, the stimuli directed at the Design Under Verification (DUV) are described as groups of instructions — each instruction carrying an operation (command) along with the associated data — rather than as raw bit patterns or as high-level scenario sequences.

It is one of three commonly distinguished levels used in constrained-random and directed stimulus generation:

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Level of Abstraction part of → 100% 1e

Command and data instruction level is one of the levels within the abstraction hierarchy.

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[1] The Command and Data Instruction Level is an intermediate abstraction level representing groups of instructions, positioned between the Sequence Level and the Bit Level. Stimuli Generation

[2] Abstraction level governs three channels: communication between user and generator, the generator's internal representation/operation level, and communication between the generator and the driver (which the driver translates into bits via the appropriate protocol). Stimuli Generation

[3] User-to-generator communication should use a level similar to that of the verification plan (e.g., the sequence level in the running example). Stimuli Generation

[4] Generators often use two or more abstraction levels: first a high-level skeleton based on user requirements, then lower-level details are added. Stimuli Generation

[5] Generator-to-driver communication generally uses the lowest level at which the generator operates. Stimuli Generation

[6] Error injection is usually done at the lowest level of abstraction by flipping the value of a bit (or set of bits) injected into the DUV, requiring the generator to also operate and communicate with the driver at the bit level. Stimuli Generation