A structured and scalable mechanism for test access to embedded reusable cores

The main objective of core-based IC design is improvement of design efficiency and time-to-market. In order to prevent test development from becoming the bottleneck in the entire development trajectory, reuse of pre-computed tests for the reusable pre-designed cores is mandatory. The core user is responsible for translating the test at core level into a test at chip level. A standardized test access mechanism eases this task, therefore contributing to the plug-n-play character of core-based design. This paper presents the concept of a structured test access mechanism for embedded cores. Reusable IP modules are wrapped in a TESTSHELL. Test data access from chip pins to TESTSHELL and vice versa is provided by the TESTRAIL, while the operation of the TESTSHELL is controlled by a dedicated test control mechanism (TCM). Both TESTRAIL as well as TCM are standardized, but open for extensions.