Configurable Boundary Scan for Secure Test Signal Access
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Solution Overview
Problem
Conventional boundary scan technology is inflexible and poses security risks due to fixed boundary scan paths and inclusion of all external pins, which can compromise test quality and security in complex systems.
Innovation Solution
Implementing a configurable boundary scan technology (C-BSCAN) that allows selective inclusion or exclusion of boundary scan cells based on configuration information, using multiplexers and programmable fuses/antifuses, and secure access through protected registers to manage signal inclusion in the boundary scan chain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional boundary scan technology is used with fixed boundary scan paths and inclusion of all external pins, then the test structure is simple and easy to implement, but the test quality and security are compromised in complex systems
Solution Approach 1:
The boundary scan path is made dynamically configurable through multiplexers that can be programmed to include or exclude specific boundary scan cells based on test requirements. This allows the same physical infrastructure to adapt its testing scope, improving test quality for complex systems without requiring multiple fixed test structures.
Solution Approach 2:
The inclusion status of boundary scan cells is changed from a fixed parameter to a configurable parameter. By programming the multiplexer select lines, the boundary scan path can be dynamically adjusted to include only relevant cells for a given test, thereby improving test quality while maintaining a simple base structure.
2Reliability
If all external pins are included in the boundary scan chain, then complete pin coverage is achieved, but security risks increase due to exposure of sensitive signals
Solution Approach 1:
Different boundary scan cells are assigned different inclusion qualities based on signal sensitivity. Critical signals can be excluded from the boundary scan chain while non-critical signals remain included, allowing the system to maintain security by protecting sensitive signals while preserving test capability for other signals.
Solution Approach 2:
Multiplexers serve as intermediary components between the boundary scan cells and the scan chain. These intermediaries act as security filters that can be configured to block sensitive signals from entering the scan chain while allowing safe signals to pass through, thus protecting security without sacrificing overall adaptability.
3Adaptability or versatility
If configurable boundary scan with multiplexers and protected registers is implemented, then test coverage and security are improved, but device complexity increases
Solution Approach 1:
The multiplexer-based configurable boundary scan structure serves multiple functions: it provides test coverage for selected signals, secures sensitive signals by excluding them from scanning, and maintains backward compatibility with conventional boundary scan modes. This multi-functionality justifies the added complexity by eliminating the need for separate test and security mechanisms.
Solution Approach 2:
The configuration of boundary scan cells is performed in advance through programming the multiplexer select lines and protected registers before actual testing begins. This preliminary configuration allows the complex structure to be simplified during operation, as the test access path is pre-determined and does not require dynamic reconfiguration during the testing process itself.
Data Source
AI summary
An embodiment of an integrated circuit may comprise first circuitry to provide a boundary scan of a signal of the integrated circuit, wherein the first circuit includes an input test data signal and an output test data signal, and second circuitry coupled to the first circuitry to selectively output one of the input test data signal and the output test data signal. Other embodiments are disclosed and claimed.