Test Vectors Considered Harmful

The Test Vector Concept A test system based on vectors has several defining characteristics: • There is a “vector sequencer” that defines which “vector” will be obeyed next. • The vector sequencer broadcasts a small amount of information (such as vector address, period numbers and timeset numbers) to all of the pin channels. • The pin channels access a small pin command, usually of between 1 and 8 bits. • The pin command, timeset and period define the set of drive and strobe events that the channel will perform. • There are limited facilities for the DUT to change the sequence of vectors. The pipelining involved in a reasonable performance test system means that pass or fail on a vector cannot affect the next n vectors to be obeyed, where n can be anywhere from 1 to 20 or more.