355:, with a default value of "100 pF" (100 picofarads). Each instance of this capacitor might also have such an attribute, only with a different value of capacitance. And other instances might not associate any capacitance at all. In the case where no capacitance is specified for an instance, the instance will "inherit" the 100 pF value from its definition. A value specified will "override" the value on the definition. If a great number of attributes end up being the same as on the definition, a great amount of information can be "inherited", and not have to be redundantly specified in the netlist, saving space, and making the design easier to read by both machines and people.
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but preserves the hierarchy dependencies. Given a hierarchical netlist, the list of instance names in a path from the root definition to a primitive instance specifies the single unique path to that primitive. The paths to every primitive, taken together, comprise a large but flat netlist that is exactly equivalent to the compact hierarchical version.
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In a "flat" design, only primitives are instanced. Hierarchical designs can be recursively "exploded" ("flattened") by creating a new copy (with a new name) of each definition each time it is used. If the design is highly folded, expanding it like this will result in a much larger netlist database,
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Folded hierarchies can be extremely compact. A small netlist of just a few instances can describe designs with a very large number of instances. For example, suppose definition A is a simple primitive, like a memory cell. Then suppose definition B contains 32 instances of A; C contains 32 instances
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Instance based netlists usually provide a list of the instances used in a design. Along with each instance, either an ordered list of net names is provided, or a list of pairs provided, of an instance port name, along with the net name to which that port is connected. In this kind of description, the
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Backannotation is data that could be added to a hierarchical netlist. Usually they are kept separate from the netlist, because several such alternate sets of data could be applied to a single netlist. These data may have been extracted from a physical design, and might provide extra information for
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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
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In large designs, it is a common practice to split the design into pieces, each piece becoming a "definition" which can be used as instances in the design. In the vacuum cleaner analogy, one might have a vacuum cleaner definition with its ports, but now this definition would also include a full
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The netlist is written in a single file, but includes four sections: 1) A file header, 2) A table listing each of the components, 3) A table listing each of the net names, 4) A table listing each of the net connections. Every table entry is written using a single line of text that ends with a
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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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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.
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of B; D contains 32 instances of C; and E contains 32 instances of D. The design now contains 5 definitions (A through E) and 128 instances. Yet, E describes a circuit that contains over a million memory cells.
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Net-based netlists usually describe all the instances and their attributes, then describe each net, and say which port they are connected on each instance. This allows for attributes to be associated with nets.
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A "folded" hierarchy allows a single definition to be represented several times by instances. An "unfolded" hierarchy does not allow a definition to be used more than once in the hierarchy.
448:. The fields of the table are separated with Space characters (0x20). String fields begin and end with double quotes. Each of the three tables are terminated by a blank line (CRLF).
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Another concept often used in netlists is that of inheritance. Suppose a definition of a capacitor has an associated attribute called "Capacitance", corresponding to the
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A definition which includes no instances is called a "primitive" (or a "leaf", or other names); whereas a definition which includes instances is "hierarchical".
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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".
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more accurate simulations. Usually the data are composed of a hierarchical path and a piece of data for that primitive or finding the values of
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you have two instances of vacuum cleaners, one might be "vac1" and the other "vac2". Besides their names, they might otherwise be identical.
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list of nets can be gathered from the connection lists, and there is no place to associate particular attributes with the nets themselves.
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The structure, complexity and representation of netlists can vary considerably, but the fundamental purpose of every netlist is to convey
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description of the machine's internal components and how they connect (motors, switches, etc.), like a wiring diagram does.
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Wolfram Alpha - sequences of
Mathematica lists encapsulated by the Analog Insydes command Netlist.
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they are connected to. A network (net) is a collection of two or more interconnected components.
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This article is about the electronics term. For the memory company, see
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SPICE ‘Quick’ Reference Sheet, THE GENERAL ANATOMY OF A SPICE DECK
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377:"Schematic vs. Netlist: A Guide to PCB Design Integration"
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is probably the most famous of the net-based netlists.
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16:Representation of electronic circuit components
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258:An "instance" could be anything from a
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359:References
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