Since these concepts are part of Verilog’s language semantics, designers could quickly write descriptions of large circuits in a relatively compact and concise form. Verilog requires that variables be given a definite size. This system allows abstract modeling of shared verilog examples with testbench pdf lines, where multiple sources drive a common net.
AND, OR, NOT, flip-flops, etc. Chi-Lai Huang and Douglas Warmke between late 1983 and early 1984. Chi-Lai Huang had earlier worked on a hardware description LALSD, a language developed by Professor S. Su, for his PhD work.
Verilog is a portmanteau of the words “verification” and “logic”. IEEE Standard 1364-1995, commonly referred to as Verilog-95. Extensions to Verilog-95 were submitted back to IEEE to cover the deficiencies that users had found in the original Verilog standard. Standard 1364-2001 known as Verilog-2001. Verilog-2001 is a significant upgrade from Verilog-95.
Verilog-2001 can instantiate an array of instances, with control over the connectivity of the individual instances. O has been improved by several new system tasks. Verilog-2005, with many new features and capabilities to aid design verification and design modeling. The current version is IEEE standard 1800-2012. Verilog is another aspect of its being a hardware description language as opposed to a normal procedural language. This is known as a “non-blocking” assignment.
Its action doesn’t register until after the always block has executed. This means that the order of the assignments is irrelevant and will produce the same result: flop1 and flop2 will swap values every clock. 1 and flop2 would not have been swapped. The definition of constants in Verilog supports the addition of a width parameter. There are several statements in Verilog that have no analog in real hardware, e.
Consequently, much of the language can not be used to describe hardware. The examples presented here are the classic subset of the language that has a direct mapping to real gates. Mux examples — Three ways to do the same thing. The output will remain stable regardless of the input signal while the gate is set to “hold”. In the example below the “pass-through” level of the gate would be when the value of the if clause is true, i.
This is read “if gate is true, the din is fed to latch_out continuously. Once the if clause is false, the last value at latch_out will remain and is independent of the value of din. Note that the else isn’t required here. When gate goes low, latch_out will remain constant. The significant thing to notice in the example is the use of the non-blocking assignment. Reset flip flop then simulation errors can result.