Language lineage

From Verilog HDL to the SystemVerilog standard family

The language moved from a proprietary origin into IEEE 1364, expanded through major revisions, and ultimately became part of the unified IEEE 1800 SystemVerilog standard.

A compact lineage

Verilog was developed at Gateway Design Automation in the 1980s as a hardware description and simulation language. Industry use expanded, and transfer to Open Verilog International helped move the language into an open standardization process. IEEE 1364-1995 established the first IEEE Verilog standard. IEEE 1364-2001 was a substantial revision, and IEEE 1364-2005 followed with further corrections and additions.

SystemVerilog extended the design and verification language around Verilog concepts, and the streams were unified under IEEE 1800. For present-day tools, “Verilog support” can therefore mean several things: an IEEE 1364 mode, a SystemVerilog mode that accepts Verilog source, or a product-specific subset. The file extension alone does not settle which parser and semantic rules are active.

VHDL is a separate hardware description language with its own IEEE standards lineage. Both languages can describe structural, register-transfer, and behavioral models, and mixed-language projects are common, but neither is merely a different spelling of the other. Their type systems, compilation models, libraries, and idioms differ, so interoperability is a tool-flow capability that must be tested.

Revision names are engineering inputs

A revision can add syntax, clarify ambiguous behavior, correct errors, and change the standard location of a feature. Tool vendors may implement revisions in stages, offer compatibility switches, or support a synthesizable subset that differs from simulator coverage. Code that compiles in a default SystemVerilog mode may not compile when a build system deliberately requests an older Verilog mode.

Teams should state the accepted language revision in build scripts and coding rules. Avoid relying on a filename convention when the compiler offers an explicit language switch. If multiple tools participate, build a compatibility suite for constructs that matter to the project: port declarations, signed expressions, generate blocks, memories, escaped identifiers, timescales, configurations, and foreign interfaces.

Separate standard meaning from project policy

The standard defines legal language behavior, but a project may intentionally permit less. Synthesizable RTL excludes many useful testbench constructs. A lint policy may ban legal constructs that are race-prone or difficult to review. A safety or portability policy may require explicit widths, reset forms, or state handling. These restrictions should be documented as policy, not described as though the language itself forbids everything outside them.

When diagnosing a disagreement, reduce the code to a small case, confirm the compiler's selected language mode, and consult both the applicable standard and the tool's release documentation. If behavior differs between implementations, preserve the commands and results. A precise language-revision statement turns “Verilog acts strangely” into a question that can be resolved.

Standards records also distinguish an active revision from superseded material and corrigenda. That status matters when a secondary source quotes a clause number or uses an older name. Cite the edition actually consulted, and avoid combining text from different revisions as though it were one document. The same discipline should appear in training material and code-review guidance.

Primary reference points

• IEEE Technology Navigator: Verilog — a concise history and standards overview.
• IEEE 1364-2005 — the Verilog hardware description language standard record.
• IEEE 1800-2023 — the current SystemVerilog unified hardware design, specification, and verification language standard record.