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VHDL was originally developed at the behest of the U. S Department of Defense in order to document the behavior of the ASICs that supplier companies were including in equipment.
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VHDL and was
In the summer of 2008, there was an intense discussion about refactoring of VHDL code on the news :// comp. lang. vhdl newsgroup.
That is to say, VHDL was developed as an alternative to huge, complex manuals which were subject to implementation-specific details.
The idea of being able to simulate this documentation was so obviously attractive that logic simulators were developed that could read the VHDL files.
The next step was the development of logic synthesis tools that read the VHDL, and output a definition of the physical implementation of the circuit.
The VHDL standard IEEE 1076-2008 was published in January 2009.
VHDL was based on the Ada programming language, as well as the experiences that had been learned with the development of ISPS earlier.
Accellera was founded in 2000 from the merger of Open Verilog International and VHDL International.
It was a hardware modelling language similar to VHDL.
The LEON family includes the first LEON1 VHSIC Hardware Description Language ( VHDL ) design that was used in the LEONExpress test chip developed in 0. 25 μm technology to prove the fault-tolerance concept.
The second LEON2 VHDL design was used in the processor device AT697 from Atmel ( F ) and various system-on-chip devices.
VHDL and at
VHDL is a dataflow language, unlike procedural computing languages such as BASIC, C, and assembly code, which all run sequentially, one instruction at a time.
In VHDL, a design consists at a minimum of an entity which describes the interface and an architecture which contains the actual implementation.
* pAVR, written in VHDL, is aimed at creating the fastest and maximally featured AVR processor, by implementing techniques not found in the original AVR processor such as deeper pipelining.
* avr_core, written in VHDL, is a clone aimed at being as close as possible to the ATmega103.
VHDL and U
In 1987, a request from the U. S. Department of Defense led to the development of VHDL ( VHSIC Hardware Description Language, where VHSIC is Very High Speed Integrated Circuit ).
In 1981, the U. S. Department of Defense began funding of VHDL as a hardware description language.
VHDL and .
The most common HDLs are VHDL and Verilog, although in an attempt to reduce the complexity of designing in HDLs, which have been compared to the equivalent of assembly languages, there are moves to raise the abstraction level through the introduction of alternative languages.
Initially the RTL description in VHDL or Verilog is simulated by creating test benches to simulate the system and observe results.
Today custom ICs and the field-programmable gate array are typically designed with Hardware Description Languages ( HDL ) such as Verilog or VHDL.
6809 cores are available in VHDL and can be programmed into FPGA and used as an embedded processor with speed ratings up to 40 MHz.
If they express much more than this, they are usually considered to be a hardware description language such as Verilog, VHDL, or any one of several specific languages designed for input to simulators.
As of late 2009, Sigasi is offering automated tool support for VHDL refactoring.
AMIQ DVT, an IDE for hardware design and verification, provides refactoring capabilities for e ( verification language ), SystemVerilog, Verilog and VHDL.
VHDL source for a signed Adder ( electronics ) | adder.
VHDL ( VHSIC 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.
Due to the Department of Defense requiring as much of the syntax as possible to be based on Ada, in order to avoid re-inventing concepts that had already been thoroughly tested in the development of Ada, VHDL borrows heavily from the Ada programming language in both concepts and syntax.
The initial version of VHDL, designed to IEEE standard 1076-1987, included a wide range of data types, including numerical ( integer and real ), logical ( bit and boolean ), character and time, plus arrays of < tt > bit </ tt > called < tt > bit_vector </ tt > and of < tt > character </ tt > called string.
Some other standards support wider use of VHDL, notably VITAL ( VHDL Initiative Towards ASIC Libraries ) and microwave circuit design extensions.
In June 2006, the VHDL Technical Committee of Accellera ( delegated by IEEE to work on the next update of the standard ) approved so called Draft 3. 0 of VHDL-2006.
While maintaining full compatibility with older versions, this proposed standard provides numerous extensions that make writing and managing VHDL code easier.
These changes should improve quality of synthesizable VHDL code, make testbenches more flexible, and allow wider use of VHDL for system-level descriptions.
VHDL and S
< source lang =" VHDL "> X <= A when S
VHDL and order
In order to directly represent operations which are common in hardware, there are many features of VHDL which are not found in Ada, such as an extended set of Boolean operators including nand and nor.
VHDL and document
Initially, Verilog and VHDL were used to document and simulate circuit designs already captured and described in another form ( such as schematic files ).
VHDL and behavior
The key advantage of VHDL, when used for systems design, is that it allows the behavior of the required system to be described ( modeled ) and verified ( simulated ) before synthesis tools translate the design into real hardware ( gates and wires ).
Another common way to write edge-triggered behavior in VHDL is with the ' event ' signal attribute.
The register transfer level ( RTL ) behavior of a digital chip is usually described with a hardware description language, such as Verilog or VHDL.
VHDL and ASICs
Designers of digital ASICs use a hardware description language ( HDL ), such as Verilog or VHDL, to describe the functionality of ASICs.
VHDL and were
Specialized HDLs ( such as Confluence ) were introduced with the explicit goal of fixing specific Verilog / VHDL limitations, though none were ever intended to replace VHDL / Verilog.
VHDL and including
Common examples of this process include synthesis of HDLs, including VHDL and Verilog.
* It is a fairly-sized VHDL project ( about 90 files, for the complete LEON2 distribution, including peripheral IP cores )
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