Net (electronics)

In electronic design, a netlist is a description of the connectivity of an electronic circuit. In its simplest form, a netlist consists of a list of the electronic components in a circuit and a list of the nodes they are connected to. A network (net) is a collection of two or more interconnected components.

The structure, complexity and representation of netlists can vary considerably, but the fundamental purpose of every netlist is to convey connectivity information. Netlists usually provide nothing more than instances, nodes, and perhaps some attributes of the components involved. If they express much more than this, they are usually considered to be a hardware description language such as Verilog or VHDL, or one of several languages specifically designed for input to simulators.

Netlists can be physical or logical, instance-based or net-based, and flat or hierarchical. The latter can be either folded or unfolded.

Most netlists either contain or refer to descriptions of the parts or devices used. Each time a part is used in a netlist, this is called an "instance".

These descriptions will usually list the connections that are made to that kind of device, and some basic properties of that device. These connection points are called "terminals" or "pins", among several other names.

An "instance" could be anything from a MOSFET transistor or a bipolar transistor, to a resistor, capacitor, or integrated circuit chip.

Instances have "terminals". In the case of a vacuum cleaner, these terminals would be the three metal prongs in the plug. Each terminal has a name, and in continuing the vacuum cleaner example, they might be "Neutral", "Live" and "Ground". Usually, each instance will have a unique name, so that if you have two instances of vacuum cleaners, one might be "vac1" and the other "vac2". Besides their names, they might otherwise be identical.

Networks (nets) are the "wires" that connect things together in the circuit. There may or may not be any special attributes associated with the nets in a design, depending on the particular language the netlist is written in, and that language's features.

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