Sharing of Topped-Off Compressed Test Sets Among Logic Blocks

Test data compression implies that a compressed test set is stored on a tester, and an on-chip decompression logic produces tests that can be applied to the circuit from compressed tests. Test data compression is used for reducing the test data volume and test application time. In a design that consists of several logic blocks, distributed test data compression refers to the case where each logic block has dedicated test data compression logic and compressed test set. Test generation procedures that are specific to this scenario attempt to share compressed tests among logic blocks to minimize the overall storage requirements. This article considers the problem of sharing a compressed test set among logic blocks when the goal is to detect faults from several different fault models. Considering a single logic block, a common practice is to consider the fault models one by one, and top off the test set as each additional fault model is considered. The sharing procedure described in this article takes advantage of the topped-off test sets of the logic blocks to consider the fault models one by one. For every fault model it considers the logic blocks one by one. This structure of the procedure provides opportunities to share compressed tests among all the logic blocks. Experimental results using benchmark circuits demonstrate the ability of the procedure to share tests for stuck-at, single-cycle gate-exhaustive and four-way bridging faults in groups of four logic blocks.