Product Documentation
Cadence VHDL-AMS Overview
Product Version 22.09, April 2022


Glossary

Across quantity

A quantity that represents the potential across two terminals.

Analog context

Anything evaluated by the analog simulator such as an analog simultaneous statement.

Architecture body

A body associated with an entity declaration to describe the internal organization or operation of a design entity. An architecture body is used to describe the behavior, data flow, or structure of a design entity. There can be multiple architecture associated with a single entity.

Attribute

A definition of some characteristic of a named entity. Some attributes are predefined for types, ranges, values, signals, and functions. The remaining attributes are user defined and are always constants.

Block

The representation of a portion of the hierarchy of a design. A block is either an external block or an internal block.

Break statement

A statement that notifies the analog solver to be prepared to deal with a discontinuity in an analog value at the next analog solution point. During a QUIESCENT_DOMAIN (DC solution), the break statement can also force named quantities to assume specified reset values.

Chip level

A level of abstraction at which a designer can perform realistic simulation of a full system:

1) Synthesis: Without any detailed timing information like FPGAs.

2) Simulation: Accurately simulates the chip.

Circuit level

Interconnected active and passive components such as resistors and capacitors.

Component

Describes instances of an entity and connects signals, quantities, and terminals to the ports of the instances.

Concurrent statement

A statement that executes asynchronously, with no defined relative order. Concurrent statements are used for dataflow and structural descriptions.

Conservative system

One that obeys Kirchhoff's laws.

Constant

An object whose value cannot be changed. Constants must be declared before they are used in models.

Continuous time simulation

A simulation in which values are a continuous function of time.

Discrete time simulation

A simulation in which all changes to the system occur at precise simulation times.

DFII

The former Cadence Design Framework II, which has now become Virtuoso Design Environment in IC 6.1.

Entity declaration

A definition of the interface between a given design entity and the environment in which it is used. Entities can also specify declarations and statements that are part of the design entity. A given entity declaration can be shared by many design entities, each of which has a different architecture. Thus, an entity declaration can potentially represent a class of design entities, each with the same interface.

Function

A collection of sequential statements that are executed for their result.

Generic

An interface constant declared in the block header of a block statement, a component declaration, or an entity declaration. Generics provide a channel for static information to be communicated to a block from its environment. Unlike constants, however, the value of a generic can be supplied externally, either in a component instantiation statement or in a configuration specification.

Generic map

The mapping between generic constants and the actual values they receive when an entity is used in a component instantiation.

Logic gate level

Corresponds directly to gate level primitives such as AND and OR.

Nature

A definition that specifies values that can be accessed through the attributes of a terminal.

Object

An named entity that has a value of a specified type. An object can be a constant, signal, variable, quantity, terminal, or file.

Package

Used to organize data and subprograms in a model.

Port

A channel for dynamic communication between a block and its environment.

Port interface list

An interface list that declares the inputs and outputs of a block, component, or design entity. The ports can be signals, quantities, or terminals.

Port map

A mapping used in component instantiations that connects actual signals, quantities, or terminals to the formal ports defined in the port interface list for the component.

Procedure

Summarizes a collection of sequential statements that are executed for their effects.

Quantity

An object with a floating point value and which has a continuous solution set by the analog solver.

Quantity port

A quantity, used to model signal flow, that is declared in a port interface list. A direction, either in or out, must be specified on quantity ports.

Reference direction

A direction determined by the order of two terminals that form a branch. For a through quantity, a positive direction represents a flow from the first terminal to the second. Similarly, for an across quantity, a higher potential on the first terminal than on the second is considered a positive potential.

Reference terminal

A terminal that is used by all terminals of a given nature as the zero for the values of its across type. Intuitively, the ground terminal for all terminals of that nature.

Register transfer level (RTL)

Systems described in the form of combinational and sequential functions such as registers, counters and decoders.

Scalar type

A type whose values have no elements. The integer, enumeration, physical, and floating point types.

Sequential statements

Statements that run in sequence.

Shared variable

A variable that can be accessed by more than one process, and by analog expressions. The order of process execution, and therefore of access to shared variables, is unspecified within any one simulation cycle.

Signal

An object with a past history of values. Signals represent interconnection wires.

Signal port

A signal, used to model signal flow, that is declared in a port interface list. Signal ports can be specified with an optional direction: in, out, inout, buffer, or linkage.

Simultaneous statements

Algebraic and differential equations used to specify the analog behavior of a system.

System level

A level of abstraction that describes a complete system.

Terminal

A point of physical connection between devices. A terminal implicitly creates two quantities: T’reference (an across quantity from this terminal to the reference terminal) and T’contribution (a through quantity from this terminal to the reference terminal).

Terminal port

A terminal, with no direction, that is declared in a port interface list. Terminal ports are used to model conservative systems.

Through quantity

A quantity that represents the flow through a terminal to a second terminal.

Variable

An object with a single current value. Variables must be declared before being used in a model.


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