2.0 Code Generation with Ptolemy

2.1 General Framework

To use Ptolemy to implement an algorithm, the problem is represented as a hierarchical dataflow graph. Two interfaces are provided: a graphical interface based on VEM, the graphic editor that is part of U.C. Berkeley's Octtools CAD system [21], and a text interface based on Ousterhout's extensible interpreter language Tcl [22]. The user builds graphs hierarchically out of existing blocks, and may also link in user-written blocks by using Ptolemy's incremental linking facility. A special preprocessor makes user-written atomic blocks (stars) easier to produce.

While this paper focuses on code generation facilities, a key feature of Ptolemy is its ability to interface different models of computation. For example, code on a DSP board can interact with a discrete-event or logic simulation running on a workstation. Similarly, a register-transfer-level simulation of hardware (complete with programmable DSPs modeled functionally) can execute generated code and process signals synthesized in another Ptolemy domain. This gives Ptolemy most of its power when applied to hardware-software codesign. The interfacing mechanism that permits one model of computation, or domain, to interface cleanly with another is called a wormhole, after the theoretical cosmological phenomenon widely used in science fiction writing that may connect widely separated regions of space, or even different universes. This mechanism is described in [6, 20], and is explained in the context of code generation in section 2.5.3.

Software Synthesis for DSP Using Ptolemy - 04 SEP 94

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