Showing papers by "Dong Xiang published in 2005"

Improving test effectiveness of scan-based BIST by scan chain partitioning

Abstract: Test effectiveness of a test-per-scan built-in self-test (BIST) scheme is highly dependent on the length and number of scan chains. Fewer cycles are used to capture test responses when the length of the scan chains increases and the total number of clock cycles is fixed. Another important feature of the test-per-scan BIST scheme is that test responses of the circuit at the inputs of the scan flip-flops are not observable during the shift cycles. A new scan architecture is proposed to make a scan-based circuit more observable. The scan chain is partitioned into multiple segments. Multiple capture cycles are inserted to receive test responses during the shift cycles compared to the test-per-scan test scheme. Unlike other BIST schemes using multiple capture cycles after the shift cycles, our method inserts multiple capture cycles inside the shift cycles, but not after the shift cycles. Unlike the previous method that drives multiple scan segments by a single scan-in signal, the proposed method uses a new architecture to control all scan segments by different signals. Sufficient experimental results are presented to demonstrate the effectiveness of the method.

Fault-tolerant routing in meshes/tori using planarly constructed fault blocks

Abstract: A few faulty nodes can make an n-dimensional mesh or torus network unsafe for fault-tolerant routing methods based on the block fault model, where the whole system (n-dimensional space) forms a fault block. A new concept, called extended local safety information in meshes or tori, is proposed to guide fault-tolerant routing, and classifies fault-free nodes inside 2-dimensional planes. Many nodes globally marked as unsafe become locally enabled inside 2-dimensional planes. A fault-tolerant routing algorithm based on extended local safety information is proposed for k-ary n-dimensional meshes/tori. Our method does not need to disable any fault-free nodes, unlike many previous methods, and this enhances the computational power of the system and improves performance of the routing algorithm greatly. All fault blocks are constructed inside 2-dimensional planes rather than in the whole system. Extensive simulation results are presented and compared with the previous methods.

Design for Cost Effective Scan Testing by Reconfiguring Scan Flip-Flops

Abstract: A new scan architecture called reconfigured scan forest is proposed for cost-effective scan testing. Multiple scan flip-flops can be grouped based on structural analysis that avoids new unstable faults due to new reconvergent fanouts. The proposed new scan architecture makes all scan flip-flop groups have similar size because of flexibility of the scan flip-flop grouping scheme, where many scan flip-flops become internal scan flip-flops. The size of the exclusive-or trees can be reduced greatly compared with the original scan forest. Therefore, area overhead and routing complexity are reduced greatly. It is shown that test application cost and test power with the proposed scan forest architecture can be reduced to even less than 1% of the conventional full scan design with a single scan chain

Scan based self-testing structure and method adopting weighted scanning strobe signal

Abstract: A self-test structure based on scan applying weight scan gating signals characterizes that the special weighted random signal generates a weighted random signal of logic output as the scanning gating signal of scanning chains in the scanning circuit, different scanning chains can correspond to different weighted values. Therefore, this invention also puts forward a method for selecting weighted values corresponding to the scanning chains separately in one weight set. This invented structure can realize the collection of test responses at any period.

Fault-tolerant routing and multicasting in hypercubes using a partial path set-up

Abstract: A new technique is proposed for fault-tolerant routing and multicasting in hypercubes by using a combination of a partial path set-up scheme and local safety information, which is a variant of the pipelined-circuit-switching (PCS). A partial path is set up for fault-tolerant routing, where the header flit is forwarded until a maximal safe subcube containing the current node and the destination is found. Similarly, a partial multicast tree is set-up for multicasting until feasible paths from the leaves of the partial multicast tree to the destinations have been guaranteed. Backtracking is adopted only for the header along the minimum paths or non-minimum feasible paths if necessary in order to set up a partial feasible multicast tree or a partial feasible path. Extensive simulation results show that the partial path set-up scheme greatly outperforms the previous fault-tolerant routing and multicasting methods while the extra latency caused by path set-up is trivial.

Using Weighted Scan Enable Signals to Improve the Effectiveness of Scan-Based BIST

Abstract: Unlike deterministic testing, it is unnecessary for scan-based BIST to apply a complete test vector into the circuit via the scan chains. A new scan-based BIST scheme is proposed by properly controlling the test signals of the scan chains. Different weighted random signals are assigned to the test signals of different scan chains. In the proposed test scheme, capture cycles can be inserted at any clock cycle. Testability calculation procedure according to the proposed testing scheme is presented. Techniques for selecting different weights on the test signals of the scan chains are also proposed. Experimental results show that the proposed method can improve the test effectiveness of scan-based BIST greatly, and most circuits can reach complete fault coverage or very close to complete fault coverage.

Fault-Tolerant Routing in Planarly Constructed Fault Blocks

Abstract: A few faulty nodes can an n-dimensional mesh or torus network unsafe for fault-tolerant routing methods based on the block fault model, where the whole system space) forms a fault block. A new concept, called extended local safety information in meshes or tori, is proposed to guide faulttolerant routing, and classifies fault-free nodes inside 2-dimensional planes. Many nodes globally marked as unsafe become locally enabled inside 2-dimensional planes. A fault-tolerant routing algorithm based on extended local safety information is proposed for k-ary n-dimensional Our method does not need to disable any fault-free nodes, unlike many previous methods, and this enhances the computational power of the system and improves performance of the routing algorithm greatly. All fault blocks are constructed inside 2-dimensional planes rather than in the whole system. Extensive simulation results are presented and compared with the previous methods. Index Terms: Computational power, fault-tolerant, routing, extended local safety, unsafe mesh torus.