Embedded Boundary Scan Controller for Processor-Independent PCB Testing
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Solution Overview
Problem
Conventional boundary scan testing of printed circuit boards relies on the functionality of the on-board processor, limiting test coverage and making it impossible to test processor-related circuitry, especially in field installations where external test equipment is not accessible.
Innovation Solution
An embedded boundary scan controller on the printed circuit board performs IEEE 1149.1 compliant testing independently of the processor, loading test vectors from non-volatile memory and storing results in on-board memory, allowing for processor-related circuitry testing without processor intervention and external equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If processor-controlled boundary scan testing is used, then testing can be performed with existing processor functionality, but test coverage is limited and processor-related circuitry cannot be tested
Solution Approach 1:
The patent divides the testing system into two independent parts: a dedicated embedded boundary scan controller that handles all testing operations, and the processor that is tested independently. This segmentation allows the boundary scan controller to operate autonomously without requiring the processor to be functional, while still enabling comprehensive testing of the processor and other circuitry.
Solution Approach 2:
The embedded boundary scan controller acts as an intermediary between external test equipment and the circuitry being tested. It receives test commands from external equipment, executes boundary scan operations, and captures results without requiring the processor to mediate these operations. This intermediary approach enables testing of the processor itself while maintaining independence from processor functionality.
2Adaptability or versatility
If external boundary scan test controllers are connected to test the processor, then complete test coverage is achieved, but field diagnostic testing becomes impossible without external equipment
Solution Approach 1:
The boundary scan controller is designed to be self-contained with all necessary testing functionality embedded on the PCB. It includes its own memory for storing test vectors and results, and can autonomously execute boundary scan operations without requiring external test equipment. This self-service capability enables complete test coverage while maintaining field diagnostic capability.
Solution Approach 2:
The embedded boundary scan controller provides multiple functions within a single integrated component: it controls boundary scan operations, stores test vectors in non-volatile memory, captures and stores test results in on-board memory, and interfaces with external equipment through standard ports. This multi-functionality achieves complete test coverage including processor-related circuitry while enabling field diagnostic testing without requiring separate external controllers.
3Productivity
If processor must be functional to run boundary scan tests, then existing processor systems can be utilized, but testing of processor-related circuitry becomes impossible
Solution Approach 1:
The patent separates the boundary scan control functionality from the processor by implementing a dedicated embedded controller. This segmentation allows the boundary scan operations to be executed independently of the processor's operational state, enabling comprehensive testing of the processor and its related circuitry without requiring the processor to be functional during testing.
Solution Approach 2:
The embedded boundary scan controller loads test vectors from non-volatile memory before executing tests, and captures results in on-board memory. This preliminary preparation and capture of test data enables complete test coverage including processor-related circuitry, while maintaining high productivity by automating the testing process without requiring manual intervention or external equipment connection during field diagnostics.
Data Source
AI summary
Embedded boundary scan testing apparatus and methodologies are disclosed for testing processor-based circuit boards without processor intervention. A boundary scan controller is embedded in a circuit board along with a boundary scan chain having JTAG devices connected with an electrical circuit of the board. Upon power up, the boundary scan controller holds an on-board processor system in reset, loads boundary scan test vectors and commands from an on-board non-volatile memory, and runs boundary scan testing while holding the processor system in the reset state. The boundary scan controller preferably includes a test access port controller that implements only a subset of the JTAG standard 16 machine states to optimize performance and minimize controller hardware. The test results may be stored in an externally accessible on-board memory for subsequent retrieval in order to facilitate board troubleshooting and/or repair, where the provision of on-board boundary scan testing allows testing of boards while installed in the field, and the embedded scan controller allows field testing of on-board processor systems and related circuitry to enhance the test coverage over processor-driven boundary scan testing.