A Hybrid Embedded Multichannel Test Compression Architecture for Low-Pin Count Test Environments in Safety-Critical Systems

This work presents a novel hybrid compression architecture that seamlessly combines the advantages of an embedded test compression technique with a lightweight codewordbased compression scheme. Embedded test compression has proven to be beneficial and is widely used in industrial circuit designs. However, particularly, in test applications within lowpin-count environments, a certain number of test patterns is incompressible and will, therefore, be rejected. This leads to a test coverage decrease which, in turn, jeopardizes the zero defect policy of safety-critical applications like automotive microcontrollers. Therefore, the rejected test patterns are typically transferred in an uncompressed way bypassing the embedded compression, which is extremely costly. The proposed hybrid architecture mitigates the adverse impact of rejected test patterns on the compression ratio as well as on the test application time of state-of-theart techniques. The experimental evaluation of industrial-sized designs clearly shows that a significant compression ratio up to 67.4% and a test application time reduction up to 72.9% can be achieved when utilizing the existing multi-channel interfaces.