Verification Plan & Levels of Verification

Verification Plan & Levels of Verification • The Verification Plan • Yesterdays and today’s design environment • Design specification document • Verification success • Levels of verification EE694v-Verification-Lect7

The Verification Plan • Just as a design meets a specification, the verification plan is the specification for the verification effort. • Defines • What is success • How a design is to be verified • Functional correctness • Which programs and testbenches to write • Schedule for verification effort EE694v-Verification-Lect7

In The Past • Verification was left to each designer to do as they wished • Verification was done as time allowed • Emphasis was “does chip work?” • Have progressed from “does chip work?” to • Does chip work in the system? • Does chip work in the system as specified? • Does the system work as specified? EE694v-Verification-Lect7

Today’s Environment • Wish to have system integration go smoothly • Simulate chip(s) in system environment to identify problems early, preferably during design and prior to fabrication • Tools that, if effectively used, can help • Simulation • Linting • Other tools EE694v-Verification-Lect7

Specifying the Verification • When will verification of design be completed to the required degree of confidence • Must determine • How much work verification will require • How many people are needed for the verification effort • How long will the verification effort take EE694v-Verification-Lect7

Design Specification Document • Verification effort relies on a complete specification document • Must be a written document • Is the common source for both the design’s implementation and its verification • When design’s output is not as expected this document helps determine whether the design is correct (verification in error) or not (verification correct) EE694v-Verification-Lect7

The Plan & 1st Time Success • The verification plan defines what success is • Insures all essential features of design are appropriately verified • Documents which features are essential and which are optional • Not all features of the final design need be included in defining 1st time success • Final success requires that all features in the final design are working and verified so. EE694v-Verification-Lect7

Levels of Verification • As the level of focus changes, what is being verified changes also • The level of granularity is also included in the plan • Best partitions to verify are those where controllability and observability are best • Controllability and observability are concepts from fault tolerance and circuit testing • Partitions being verified must have relatively stable functionality and interfaces EE694v-Verification-Lect7

Unit-Level Verification • Design units are logical partitions and vary from small to large, simple to complex • Small/Simple - FIFO, small state machine • Large/Complex - PCI slave interface, DSP datapath • Often have interfaces that are not fixed and firm • The interface many be configurable for the application • Often functionality is not yet fixed and firm • Any reasonable size project will have a large number of design units • Verification of the entire design at this level would probably be too time consuming EE694v-Verification-Lect7

Reusable Component Verification • Component is designed to its own specification • Component intended to be used as-is in many different designs • Typically the component implements a common function or allows connection to a standardized interface • Component is used in many designs - focus is on its functionality • Potential users must have confidence that design is indeed correct EE694v-Verification-Lect7

ASIC & FPGA Verification • These units form a physical and possibly a logical partition • Often have their own specification • Often contain a collection of independently designed and verified components • Todays ASICs and FPGAs are too complex to verify and debug during integration. Need verification for them prior to synthesis or downloading the programming. EE694v-Verification-Lect7

System-Level Verification • There are many definitions for a system!!! • In the book - “a system is a logical partition composed of independently verified components.” • System could be • composed of a few reusable components • a subset of an SoC ASIC • ASICs (or part of ASICs) on different boards • Focuses on interaction between components • Relies on individual components being functionally correct EE694v-Verification-Lect7

Board-Level Verification • Confirm that component connectivity is correct • Some components on boards, such as capacitors, do not translate easily to digital domain • Depending on the complexity level, could be used to verify functionality (as with any other level) • Must make sure what is verified is what is manufactured (as with all levels) EE694v-Verification-Lect7

Development of a Verification Plan • Factors that are important • Level of verification • Level of complexity of the unit/system • Type of unit/system • Level of confidence needed • Must analyze the operational space in analyzing the level of confidence that can be placed in the verification effort. EE694v-Verification-Lect7

Plan Content • What goes into verification plan? • Description of what is to be verified • Analysis of tests to be applied • Divided up into sets to test the various aspects of the test domain space • An analysis of the complete test space and how the various aspects interface • For example – two normalized numbers can produce overflow to infinity, zero, a denormalized number even though in most cases it results in a normalized result. EE694v-Verification-Lect7

Plan Content • How are the tests to be generated • Test sets and the program(s) to generate them are specified. • Test to adequately tests for the regions identified • Most likely also generate the expected result so that self checking can be done. • The Testbench(s) that will be used to apply the tests and check the results. (self checking) • How will it be constructed. Will the tests be integral to the testbench or read from a file. EE694v-Verification-Lect7

The Plan (cont) • Essential elements of the plan • Definition of Verification Success • How do you know you are done? When have you tested enough? • This is formally defined in the Verification Plan • Verification Schedule • A pert chart with the tasks and a schedule for the tasks assigned to members of the team. • A failure to plan is a plan to …….. EE694v-Verification-Lect7

Verification Plan & Levels of Verification