Test Mode Control Circuit for Unauthorized Access Prevention
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Solution Overview
Problem
Existing test mode control circuits for semiconductor chips lack effective mechanisms to prevent unauthorized access to vendor-specific test modes, which can lead to faulty operations or malfunctions during normal operations.
Innovation Solution
A test mode control circuit that includes a signal generation circuit and serially-connected latch circuits, generating set and reset signals in response to code signals and a mode register signal to control the entry into a vendor-specific test mode, ensuring only authorized vendor code sequences can initiate the test mode, thereby preventing unauthorized access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a simple test mode control mechanism is used, then the circuit operation is simple and fast, but unauthorized access to vendor-specific test mode cannot be prevented
Solution Approach 1:
The test mode control circuit is divided into multiple serially-connected latch circuits (first latch circuit, second latch circuit, third latch circuit), each handling a portion of the code sequence verification. This segmentation allows the system to implement a complex security protocol while maintaining modular circuit design and enabling sequential processing of authorization codes.
Solution Approach 2:
The circuit requires preliminary input of a specific code sequence through the latch circuits before the vendor-specific test mode can be activated. The mode register signal is held in a disabled state until the correct code sequence is sequentially input and stored in the latch circuits, preventing unauthorized premature activation.
2Reliability
If a code sequence verification mechanism is implemented, then unauthorized access is prevented, but the entry process becomes more complex and time-consuming
Solution Approach 1:
The code sequence verification is performed through periodic clocked operations of the latch circuits. Each latch circuit captures its respective code bit at specific clock cycles, allowing the verification process to be completed in a predetermined number of clock periods rather than requiring continuous monitoring or complex real-time analysis.
3Adaptability or versatility
If vendor-specific test mode is accessible, then testing capability is enhanced, but faulty operations or malfunctions may occur during normal operations
Solution Approach 1:
The mode register acts as an intermediary between the normal operation mode and the vendor-specific test mode. The mode register signal serves as a controlled interface that can transition the circuit between states, allowing authorized access to testing functionality while preventing direct or unauthorized entry that could cause operational errors.
Data Source
AI summary
A test mode control circuit relating to a technology for controlling a vendor specific test mode is disclosed. The test mode control circuit includes a signal generation circuit configured to generate a plurality of set signals and a plurality of reset signals in response to a plurality of code signals and a predetermined mode register signal; and a plurality of serially-connected latch circuits configured to selectively operate in response to the plurality of set signals and the plurality of reset signals so as to control an entry signal of an output terminal.