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The four values are 1, 0, Z and X. 1 and 0 stand for Boolean true and false, Z stands for high impedance or open circuit and X stands for don't care (e.g., the value has no effect). This logic is itself a subset of the 9-valued logic standard called IEEE 1164 and implemented in Very High Speed Integrated Circuit Hardware Description Language ...
Verilog-2001 is a significant upgrade from Verilog-95. First, it adds explicit support for (2's complement) signed nets and variables. Previously, code authors had to perform signed operations using awkward bit-level manipulations (for example, the carry-out bit of a simple 8-bit addition required an explicit description of the Boolean algebra ...
value_if_true : value_if_false. The condition is evaluated true or false as a Boolean expression. On the basis of the evaluation of the Boolean condition, the entire expression returns value_if_true if condition is true, but value_if_false otherwise. Usually the two sub-expressions value_if_true and value_if_false must have the same type, which ...
For example, because true OR true equals true, and true OR false also equals true, then true OR unknown equals true as well. In this example, because either bivalent state could be underlying the unknown state, and either state also yields the same result, true results in all three cases.
In Boolean logic, the majority function (also called the median operator) is the Boolean function that evaluates to false when half or more arguments are false and true otherwise, i.e. the value of the function equals the value of the majority of the inputs.
XOR gate (sometimes EOR, or EXOR and pronounced as Exclusive OR) is a digital logic gate that gives a true (1 or HIGH) output when the number of true inputs is odd. An XOR gate implements an exclusive or from mathematical logic; that is, a true output results if one, and only one, of the inputs to the gate is true.
Register-transfer-level abstraction is used in hardware description languages (HDLs) like Verilog and VHDL to create high-level representations of a circuit, from which lower-level representations and ultimately actual wiring can be derived. Design at the RTL level is typical practice in modern digital design.
SystemVerilog for register-transfer level (RTL) design is an extension of Verilog-2005; all features of that language are available in SystemVerilog. Therefore, Verilog is a subset of SystemVerilog. SystemVerilog for verification uses extensive object-oriented programming techniques and is more closely related to Java than Verilog. These ...