Shared Wrapper Cell Scan-Capture Control for SoC Fault Coverage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Complex integrated circuit (IC) designs often result in incomplete fault detection due to wrapper cells blocking fault propagation in both in-test and ex-test modes of automatic test pattern generation (ATPG), leading to significant coverage loss in system-on-chip (SoC) testing.
Innovation Solution
A control circuit is employed to enable directional control of scan capture through shared wrapper cells, utilizing logic gates to configure the direction of scan capture based on selected test modes, allowing fault activation and observation in both in-test and ex-test modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wrapper cells are used for scan capture in ATPG testing, then test mode functionality is provided, but fault propagation is blocked in both in-test and ex-test modes
Solution Approach 1:
The wrapper cell is designed with dynamic reconfigurability, allowing it to change its operational state based on the selected test mode. Control logic dynamically adjusts the wrapper cell's behavior to either capture faults from the core or from the interface, enabling adaptive fault propagation paths that were previously blocked in static wrapper designs
Solution Approach 2:
The wrapper cell's operational parameters are changed based on test mode selection signals. By modifying control parameters such as scan enable conditions and capture timing based on whether in-test or ex-test mode is selected, the wrapper cell transitions from blocking fault propagation to enabling it in the appropriate direction
2Device complexity
If one-way scan capture is used in wrapper cells, then simple test mode operation is achieved, but fault detection in both directions is prevented
Solution Approach 1:
The wrapper cell is designed to perform multiple functions within a single structure. It can capture faults from the core in in-test mode and from the interface in ex-test mode, effectively making it a universal test interface that handles both directional fault detection requirements without requiring separate wrapper cells for each direction
3Productivity
If shared wrapper cells are used for both in-test and ex-test modes, then resource efficiency is improved, but mode-specific control is lost
Solution Approach 1:
The shared wrapper cell incorporates dynamic control logic that responds to test mode selection signals. The control circuitry automatically configures the wrapper cell's behavior according to the active test mode, maintaining ease of operation through automated mode-specific control while preserving resource efficiency through sharing
Solution Approach 2:
A control logic intermediary is introduced between the test mode selection and the shared wrapper cell. This intermediary translates high-level mode selection into specific control signals that configure the wrapper cell appropriately for each mode, bridging the gap between resource sharing and mode-specific operation requirements
Data Source
AI summary
Aspects of directional control of scan capture through shared wrapper cells are disclosed. For example, a control circuit of an integrated-circuit IC can enable the directional control of scan captures through a shared wrapper cell. The control circuit can receive a selection of a mode for testing the IC and, based on the selection of the mode, the control circuit configures logic of a shared wrapper cell to control a direction of a scan capture through the shared wrapper cell for the selected test mode. The scan capture for the selected test mode is applied to the shared wrapper cell and an output of the scan capture through the shared wrapper cell is determined for the selected test mode. By so doing, the described aspects may enable fault activation or fault observation for logic that could not be previously tested due to the one-way nature of many test modes.