Chapter 1 - Introduction

Overview

The ProtoCollum tool is built to facilitate visual protocol modeling. The tool has taken the Message Sequence Chart (MSC) technique for displaying message flow over time and expanded it into a fully interactive visual design entry and simulation tool.

ProtoCollum is designed to be a general tool for modeling of any protocol; from small proprietary intra-chip protocols which specifiy unit-to-unit signaling, to large communication protocols maintained by standard committees. The tool provides value wherever understanding of a given protocol can be enhanced by improved visualization of the protocol design and behavior.

Architecture Capture (Edit Sheet)

As illustrated in the diagram, a protocol architecture is captured on an Edit Sheet by specifying the Processing Entities (PE), Messages, and Rules for the desired message passing system. Timing requirements can also be specified as part of a Rule. These objects become an executeable model of the protocol architecture.

Message Sequencing (Test Sheet)

Once the protocol architecture is specified, the Test Sheet is used to run or execute the protocol model. The Test Sheet is similar in layout to a MSC. In the vertical are shown PEs which send and receive messages. In the horizontal are shown Messages being sent and received. Time flows from top to bottom; messages at the top of the chart were sent before messages at the bottom.

However, unlike a typical Message Sequence Chart, the Test Sheet is a fully interactive simulation of the protocol architecture. As the user interactively connects, disconnects, and reconnects messages to establish the desired exact order of events, the system runs an execution loop to determine the new status of the PEs. It is the order of message arrival that determines the behavior of a PE in a message passing system.

Tool Applications

By using Edit and Test Sheets to do protocol capture, protocol execution and testing, and then coming back to refine the protocol, a designer can create a protocol specification and have confidence that it will function as intended. A ProtoCollum description can replace an ambiguous english language protocol specification with an accurate, visual, interactive specification.

The executeable model created by ProtoCollum can be used for any number of design and validation activities. A validation team could use the executeable model as a Checker by converting results of functional unit simulation (i.e. at the RTL level) to messages which may be tested at the architectural level by ProtoCollum.