Difference Between HDL VHDL, Verilog, SystemVerilog; UPF
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What is the Difference Between HDL, VHDL, Verilog, SystemVerilog; UPF? The Designers of electronic hardware describe the behavioral structure
of system circuit designs using hardware description languages
(HDLs).
This, (HDL), is a specialized programming languages commonly known as today as VHDL,
Verilog, SystemVerilog, and the added UPF language is the missing link.
SystemVerilog (which includes Verilog 2001), VHDL, and UPF
are parsed and processed in two steps, analysis and elaboration. Mixed
VHDL and SystemVerilog compilation is fully supported via UPF.
This Elaboration supports both static elaboration and RTL elaboration.
Static elaboration elaborates
the entire language that specifically binds instances to modules,
resolves library references, propagates defparams, unrolls generate
statements, and checks all hierarchical names/function/task calls. The
result after static elaboration is an elaborated parse tree,
appropriate for application simulations.
RTL elaboration is
limited to the synthesize subset of the language. In addition to the
static elaboration tasks for this subset, it generates sequential
networks through flipflop and latch detection, and Boolean extraction.
The result after RTL elaboration is a netlist, appropriate for
applications such as logic synthesis and formal verification.
The netlist database stores RTL and netlist designs
in a language-independent simple model based on generic gates such as
The DFF, The AND, The OR, The MUX , etc.. The netlist database is common to both VHDL
and SystemVerilog and has an efficient and clean API for easy
integration into any existing database or object model.
- Very memory efficient. Average overall memory usage just 300 bytes/gate.
- Full hierarchy support, with grouping/ungrouping, etc.
- Support for buses.
- Compact storage of file/line/column origination info from RTL parsers.
- Simple and clean data model and procedural Interface for easy integration with your existing database.
HDL: hardware description language (HDL) , In computer engineering, is a specialized computer language used to describe the structure and behavior of electronic circuits, and most commonly, digital logic circuits. A hardware description language enables a precise, formal description of an electronic circuit that allows for the automated analysis and simulation of an electronic circuit. It also allows for the synthesis of a HDL description into a netlist (a specification of physical electronic components and how they are connected together), which can then be placed and routed to produce the set of masks used to create an integrated circuit. A hardware description language looks much like a programming language such as C;
it is a textual description consisting of expressions, statements and
control structures. One important difference between most programming
languages and HDLs is that HDLs explicitly include the notion of time. HDLs form an integral part of electronic design automation (EDA) systems, especially for complex circuits, such as application-specific integrated circuits, microprocessors, and programmable logic devices.
SystemVerilog, standardized as IEEE 1800, is a hardware description and hardware verification language used to model, design, simulate, test and implement electronic systems. SystemVerilog is based on Verilog and some extensions, and since 2008 Verilog is now part of the same IEEE standard. It is commonly used in the semiconductor and electronic design industry as an evolution of Verilog.
Verilog, standardized as IEEE 1364, is a hardware description language (HDL) used to model electronic systems. It is most commonly used in the design and verification of digital circuits at the register-transfer level of abstraction. It is also used in the verification of analog circuits and mixed-signal circuits, as well as in the design of genetic circuits.[1] In 2009, the Verilog standard (IEEE 1364-2005) was merged into the SystemVerilog
standard, creating IEEE Standard 1800-2009. Since then, Verilog is
officially part of the SystemVerilog language. The current version is
IEEE standard 1800-2017.[2]
VHDL (VHSIC-HDL) (Very High Speed Integrated Circuit Hardware Description Language) is a hardware description language used in electronic design automation to describe digital and mixed-signal systems such as field-programmable gate arrays and integrated circuits. VHDL can also be used as a general purpose parallel programming language.
It natively interfaces with Verific’s data
structures, and also has the ability to interface with external
(non-Verific) design data.
The UPF Parser/Analyzer performs syntax and
semantic checking, resolving a UPF specification into a power intent
model that can be traversed and queried.
Complete file / line / column
information on UPF descriptions is maintained and Verific’s
comprehensive error handler is included.
The UPF Elaborator applies the power intent model to the original HDL
design.
The result is a power-aware netlist with new instantiations of
power-related cells, as well as any required supply network and
corresponding control path logic.
UPF concepts elaborated in an HDL
design include logic and supply ports and nets, power switches, and
retention, isolation, level-shifter and repeater cells.
Verific’s UPF parser is also easily integrated with external (non-Verific) data structures.
Analysis creates parse-trees and performs
type-inferencing to resolve the meaning of identifiers.
The
Parser/Analyzer modules support the entire SystemVerilog IEEE 1800
(including Verilog IEEE 1364), VHDL IEEE 1076, and UPF IEEE 1801
languages, all revisions, without any restrictions. The resulting parse
trees / data models come with extensive APIs.
They differ from software programming
languages because they include a means of describing propagation time
and signal strengths.
These days, (2019-*), it would be impossible to design a
complex system on a chip (SoC) for a mobile device or any other consumer
electronics product without an HDL.
Each of the three HDLs has its own distinct
style.
VHDL and Verilog implement register-transfer-level (RTL)
abstractions.
When they were first introduced in the late 1980s, they
were considered breakthrough technologies because they enabled engineers
to work at a higher level of abstraction with RTL simulators.
Previously, engineers simulated their designs at the schematic or gate
level.
SystemVerilog was developed to provide an evolutionary path from VHDL and Verilog to support the
complexities of SoC designs.
It’s a bit of a hybrid—the language
combines HDLs and a hardware verification language using extensions to
Verilog, plus it takes an object-oriented programming approach.
SystemVerilog includes capabilities for test-bench development and
assertion-based formal verification.
The U.S. Department of Defense funded VHDL, and Gateway Design
Automation developed Verilog to drive the Verilog simulator.
Cadence
Design Systems, once it acquired Gateway, placed the Verilog HDL into
the public domain and it became an industry standard.
In the early 1990s, the electronics industry was forced to contend
with the “language wars,” where competing factions in either the VHDL or
Verilog camp competed for an engineer’s desktop mindset.
Both
languages survived and now coexist, often in the same design flow -i.e. Xilinx.com.
Co-Design designed SystemVerilog, initially known as SUPERLOG.
After
Synopsys acquired Co-Design, SUPERLOG/SystemVerilog was placed in the
public domain as well.
All three are IEEE industry standards –– VHDL is IEEE 1076-2008,
Verilog is IEEE 1364-2005 and SystemVerilog is IEEE 1800-2012.
The IEEE
works cooperatively with the industry standards organization Accellera,
which acts as its steward and develops many of IEEE’s technology
standards for system-level design, modeling, and verification.
My company, (Rob Dekker, CTO & Founder, Verific Design Automation ), Verific Design Automation, has built parsers and elaborators for VHDL, Verilog, and SystemVerilog since 1999.
Comparing VHDL, Verilog, SystemVerilogVHDL and Verilog are considered general-purpose digital design
languages, while SystemVerilog represents an enhanced version of
Verilog.
Each has its own style and characteristics.
VHDL has roots in
the Ada programming language in both concept and syntax, while Verilog’s
roots can be tracked back to an early HDL called Hilo and the C
programming language.
VHDL is a rich and strongly typed language, deterministic and more
verbose than Verilog.
With Verilog and VHDL, engineers can represent the desired
functionality as a software program.
Then the model is simulated to
confirm the design will work as intended.
Any problems can be corrected
in the model, and simulation will verify the correction.
As a result, designs written in VHDL are
considered self-documenting.
Its syntax is non-C-like and engineers
working in VHDL need to do extra coding to convert from one data type to
another.
VHDL often catches errors missed by Verilog.
VHDL emphasizes
unambiguous semantics and allows portability between tools.
Sample VHDL Code:
reg1: process (rst, clk)
begin
if rst = '1' then
q_reg <= (others => '0');
q_i <= (others => '0');
elsif rising_edge(clk) then
if s_l = '1' then
q_i(0) <= q_i(7);
loop1: for i in 6 downto 0 loop
q_i(i + 1) <= q_i(i);
end loop loop1;
q_reg <= y;
else
q_i <= q_reg;
q_reg <= y;
end if;
end if;
end process reg1;
Verilog
is weakly typed and more concise with efficient notation.
It is
deterministic.
All data types are predefined in Verilog and each has a
bit-level representation.
Syntax is C-like.
Sample Verilog Code:
always @(posedge CLK or posedge RST)
begin
if (RST) begin
q_reg = 0;
Q = 0;
end else if (S_L) begin
Q[7:0] = {Q[6:0],Q[7]};
q_reg = Y;
end else begin
Q = q_reg;
q_reg = Y;
end
end
SystemVerilog includes a set of extensions to the Verilog HDL to help
engineers design and verify larger and more complex designs.
In fact,
many industry watchers consider it the first Hardware Description and
Verification Language (HDVL), because it combines VHDL and Verilog
features with those of Hardware Verification Languages (HVLs) Vera and e,
as well as C and C++.
It’s targeted at RTL coding, using constrained
random techniques for assertion-based and coverage-driven verification.
Sample SystemVerilog Code:
property p_push_error;
@ (posedge clk)
not (b_if.push && b_if.full && !b_if.pop);
endproperty : p_push_error
ap_push_error_1 : assert property (p_push_error);
property p_pop_error;
@ (posedge clk)
not (b_if.pop && b_if.empty);
endproperty : p_pop_error
ap_pop_error_1 : assert property (p_pop_error);
always_ff @ (posedge clk) begin
b_if.error <= (b_if.pop && b_if.empty) || (b_if.push && b_if.full && !b_if.pop);
Because of its structure, VDHL catches most errors early in the
design process.
Verilog, on the other hand, enables engineers to quickly
write models.
SystemVerilog attempts to capture the best features of
both, and includes features of HVLs to support test-bench development and
formal verification techniques.
