About ADS Ptolemy

The ADS Ptolemy software provides the simulation tools you need to evaluate and design modern communication systems products. Today's designs call for implementing DSP algorithms in an increasing number of portions in the total communications system path, from baseband processing to adaptive equalizers and phase-locked loops in the RF chain. Cosimulation with ADS RF and analog simulators can be performed from the same schematic.

Using the ADS Ptolemy simulator you can:

• Find the best design topology using state-of-the-art technology with more than 500 behavioral DSP and communication systems models
• Cosimulate with RF and analog simulators
• Integrate intellectual property from previous designs
• Reduce the time-to-market for your products

And, ADS Ptolemy features:

• Timed synchronous dataflow simulation
• Easy-to-use interface for adding and sharing custom models
• Interface to test instruments
• Data display with post-processing capability

ADS Ptolemy and UC Berkeley Ptolemy

The Ptolemy signal processing simulator has its roots at the University of California at Berkeley. UC Berkeley Ptolemy is a third-generation software environment that began in January of 1990. It is an outgrowth of two previous generations of design environments, Blosim and Gabriel, that were aimed at digital signal processing. Both environments use dataflow semantics with block-diagram syntax for the description of algorithms.

Built on the UC Berkeley Ptolemy code, ADS Ptolemy software includes a large number of behavioral, time-domain antenna and propagation models that are critical to communication systems designers. For DSP designers, fixed-point analysis is scalable up to 256 bits. The intuitive ADS user interface includes post-processing capability, cosimulation with analog/RF simulators, links to test instruments, online help, and a host of other features.

In Ptolemy, different specialized design environments are called domains. ADS Ptolemy has modified the proven synchronous dataflow domain to include timed components; this is called the timed synchronous dataflow domain.

Timed Synchronous Dataflow Simulator

The timed synchronous dataflow domain captures years of Agilent EEsof expertise in system-level analog/RF simulation, while adding the benefits of dataflow technology. This domain enables fast RF simulation, integration with signal processing simulation, and cosimulation with Agilent EEsof circuit simulators. For more information on the timed synchronous dataflow simulator and the synchronous dataflow domain, refer to Theory of Operation for ADS Ptolemy Simulation.

Terminology

Throughout most of the ADS Ptolemy documentation, we use the ADS terminology, which is standard EDA terminology. However, UC Berkeley Ptolemy has its own terminology and for users familiar with this terminology, or those who are writing their own models, the following table compares the terms. The UC Berkeley Ptolemy terminology is used only in Theory of Operation for ADS Ptolemy Simulation and in the topics on building signal processing models found in the User-Defined Models documentation.

Terminology Comparison

ADS Ptolemy Term	UC Berkeley Ptolemy Term
Component	Star
Network (or circuit)	Galaxy
Top-level System	Universe
Controller	Target
Wire	Arc
Data (or signals)	Particles (or tokens)

$HPEESOF_DIR

In UNIX installations, the environment variable specifying the directory in which the ADS software is installed. In Windows installations, the syntax, when needed, is %HPEESOF_DIR%.

actor

An atomic (indivisible) function in a dataflow model of computation. An actor is called a component in ADS Ptolemy and a star in UCB Ptolemy.

arc

A wire that connects the output of one star or component with the input of another.

base class

A C++ object used to define common interfaces and common code for a set of derived classes. An object may be a base class and a derived class simultaneously.

behavioral modeling

System modeling consisting of functional specification plus modeling of the timing of an implementation (compare to functional modeling).

Block

The base class defined in the kernel for stars, galaxies, universes, and targets.

block

A star or a galaxy.

compile-time scheduling

A scheduling policy in which the order of block execution is pre-computed when the execution is started. The execution of the blocks thus involves only sequencing through this pre-computed order one or more times (compare to run-time scheduling).

derived class

A C++ object derived from some base class. It inherits all of the members and methods of the base class.

dataflow

A model of computation in which actors process streams of tokens. Each actor has one or more firing rules. Actors that are enabled by a firing rule may fire in any order.

domain

A specific implementation of a computation model.

Domain

The base class in the ADS Ptolemy kernel from which all domains are derived.

drag

The action of holding a mouse button while moving the mouse.

FFT

The Fast Fourier Transform (FFT) is an efficient way to implement the discrete Fourier transform in digital hardware.

firing

A unit invocation of an actor in a dataflow model of computation.

firing rule

A rule that specifies how many tokens are required on each input of a dataflow actor for that actor to be enabled for firing.

fork star

A star that reads one input particle and replicates it on any number of outputs.

functional modeling

System modeling that specifies input/output behavior without specifying timing (compare to behavioral modeling).

galaxy

A block that contains a network of other blocks.

Gantt chart

A graphical display of a parallel schedule of tasks. In ADS Ptolemy, the tasks are the firings of stars and galaxies.

homogeneous synchronous dataflow

A particular case of the synchronous dataflow model of computation, where actors produce and consume exactly one token on each input and output.

hpeesoflang

• A schema language used to define stars in ADS Ptolemy.
• The program that translates stars written in the hpeesoflang language to C++. In UCB Ptolemy, the equivalent language is called ptlang.

iteration

A set of executions of blocks that constitutes one pass through the pre-computed order of a compile-time schedule.

kernel

The set of classes defined in the ADS Ptolemy kernel.

layer

In the Schematic, a color with a given precedence. Colors with higher precedence will obscure colors with lower precedence.

member

A C++ object that forms a portion of another object.

method

A function defined to be part of an object in C++.

model of computation

A set of semantic rules defining the behavior of a network of blocks.

net

A graphical connection between ports in the schematic.

object

A data type in C++ consisting of members and methods. These members and methods may be private, protected, or public. If they are private, they can only be accessed by methods defined in the object. If they are protected, they can also be accessed by methods in derived classes. If they are public, they can be accessed by any C++ code.

palette

A schematic area that contains a library of block icons.

parameter

The initial value of a state.

particle

Data (for example, a floating-point value) communicated between blocks.

port

A star or galaxy input or output.

PortHole

The base class in the ADS Ptolemy kernel for all ports.

Ptolemy

A design environment that supports simultaneous mixtures of different computation models. Ptolemy, named after the second-century Greek astronomer, mathematician, and geographer, was developed at the University of California at Berkeley.

real time

The actual time (compare to simulated time).

RTL

Register-transfer level description of digital systems.

run-time scheduling

A scheduling policy in which the order of block execution is determined on-the-fly , as they are executed (compare to compile-time scheduling).

Scheduler

An object associated with a domain that determines the order of block execution within the domain. Domains may have multiple schedulers.

schematic

A block diagram.

SDF

A simulation domain using the synchronous dataflow model of computation.

simulated time

In a simulation domain, the real number representing time in the simulated system (compare to real time).

simulation

The execution of a system specification (an ADS Ptolemy block diagram) from within the ADS Ptolemy process (that is, execution without generating code and spawning a new process to execute that code).

simulation domain

A domain that supports simulation, but not code generation.

star

A component in ADS Ptolemy. An atomic (indivisible) unit of computation in an ADS Ptolemy application. Every ADS Ptolemy simulation ultimately consists of executing the methods of the stars used to define the simulation.

Star

The base class in the ADS Ptolemy kernel for all stars.

state

A member of a block that stores data values from one invocation of the block to the next.

State

The base class in the ADS Ptolemy kernel for all states.

stop time

Within a timed domain, the time at which a simulation halts.

symbol

A graphical object that represents a single block.

synchronous dataflow

A dataflow model of computation where the firing rules are particularly simple. Every input of every actor requires a fixed, pre-specified number of tokens for the actor to fire. Moreover, when the actor fires, a fixed, pre-specified number of tokens is produced on each output. This model of computation is particularly well-suited to compile-time scheduling.

target

An object that manages the execution of a simulation or code generation process. In ADS Ptolemy this is called a controller. For example, in code generation, the target would be responsible for compiling the generated code and spawning the process to execute that code.

Target

The base class in the kernel for all targets.

Tcl

Tool command language-a textual, interpreted language developed by John Ousterhout at UC Berkeley. Tcl is embedded in ADS Ptolemy.

timestamp

A real number associated with a particle in timed domains that indicates the point in simulated time at which the particle is valid.

timed domain

A domain that models the evolution of a system in time.

Tk

A Windows and X-Windows toolkit for Tcl. The interactive sliders, buttons, and plotting capabilities of ADS Ptolemy are implemented in Tcl/Tk.

token

A unit of data in a dataflow model of computation. Tokens are implemented as particles in ADS Ptolemy.

universe

An entire ADS Ptolemy design.

VHDL

The VHSIC hardware description language, a standardized language for specifying hardware designs at multiple levels of abstraction.

wormhole

A star in a particular domain that internally contains a galaxy in another domain.