IC Test Mode Switching via TAP Controller States
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Solution Overview
Problem
Existing integrated circuits require additional terminals for switching test units between operating modes, making them more time-consuming and costly to produce, and preventing functionality testing after mounting on a printed circuit board.
Innovation Solution
The integrated circuit connects the gate terminal of the test unit to the TAP controller, allowing mode switching based on internal states, eliminating the need for dedicated terminals and enabling functionality testing both during production and after mounting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If additional separate terminals are provided for switching the test unit between operating modes, then the test unit can be controlled to switch between modes, but the realization of the integrated circuit becomes more time-consuming and costly
Solution Approach 1:
The patent merges the mode switching function with the existing JTAG interface by connecting the gate terminal to the TAP controller. The TAP controller's internal states are used to control the multiplexer selections, eliminating the need for separate switching terminals. This combines two functions (testing and mode switching) into a single integrated control mechanism, reducing manufacturing complexity while maintaining operational capability.
2Ease of operation
If additional separate terminals are provided for switching the test unit between operating modes, then the test unit can be controlled to switch between modes, but the functionality of the functional units cannot be tested when the integrated circuit is mounted on a printed circuit board
Solution Approach 1:
The patent makes the JTAG interface universal by enabling it to serve dual purposes: normal operational testing and mode switching for the test unit. The TAP controller is designed to control both the functional units and the multiplexer selections, allowing the same interface to be used for testing whether the integrated circuit is standalone or mounted on a printed circuit board, thereby achieving multi-functionality and post-mounting adaptability.
3Device complexity
If terminals of the integrated circuit are used for both normal output signals and test signals, then no additional terminals are needed, but the functionality of the functional units cannot be tested after mounting on a printed circuit board
Solution Approach 1:
The patent introduces dynamic control of terminal functionality through the TAP controller. The same terminals are dynamically assigned to different functions based on the operational mode: in normal mode, they serve as output signals; in test mode, controlled by TAP controller states, they serve as test signal paths. This dynamic reconfiguration enables post-mounting testing without requiring additional dedicated terminals, as the terminal roles change based on control signals rather than fixed assignments.
Data Source
AI summary
The invention relates to an integrated circuit for a data transmission system comprising a) a plurality of functional units, b) a TAP controller, according to IEEE 1149, having a JTAG interface, and c) a test unit for testing the functionality of the functional units, whereby the test unit has at least two operating modes and at least one gate terminal for switching between the operating modes and is designed to connect circuit points, assigned to a specific operating mode, of the functional units to terminals of the integrated circuit, when the test unit is operated in the specific operating mode. According to the invention, the at least one gate terminal of the test unit is connected to the TAP controller and the integrated circuit is designed to switch between the operating modes depending on the internal states of the TAP controller. The invention relates furthermore to a receiving device of a data transmission system.