Testability and test protocol expansion in hierarchical macro testing

Test protocols play an important role within the macro tests strategy. They describe, independently of the actual test pattern values and in detail how, at which terminals, and at which moments tests stimuli should be applied and responses should be observed. Initially, test protocols are described at the terminals of the macro they test. Final execution should take place at the chip pins. Transforming a test protocol defined at the (local) macro terminals into a test protocol defined at the (global) chip pins is called test protocol expansion. Failing test protocol expansion indicates testability problems of the circuit under consideration