Testability analysis and scalable test generation for high-speed floating-point units

High-speed datapaths in microprocessors and embedded processors contain complex floating-point ( FP) arithmetic units which have a critical role in the processor's performance. Although the FP units' complex structure consists of classic integer arithmetic components, the embedded components encounter serious testability problems due to their limited accessibility from the FP unit ports and testability loss due to FP unit inherent operations, such as rounding and normalization. In this paper, we analyze the testability problems and present scalable test generation for FP units using as a demonstration vehicle the popular, high-speed, two-path architecture of the most complex unit, the FP adder. The key feature of the presented methodology is the identification of testability conditions that guarantee effective test pattern application and fault propagation for each of the components of the FP adder. The identified test conditions can be utilized with respect to any fault model and are independent of the internal structure and the size of the components. Thus, they can be applied to FP adders of various exponent and significand sizes ( single, double, and custom precision), as well as to other types of FP units, which also consist of classic integer arithmetic components similarly interconnected.