Addressable Test Access Port with Command Capability
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Solution Overview
Problem
Current IEEE 1149.1 standard Test Access Ports (TAPs) lack the ability to address and command devices effectively beyond the Run Test/Idle state, leading to increased wiring complexity and limited functionality in device access operations.
Innovation Solution
The introduction of a control bit on the Test Data Input (TDI) signal allows for addressing and commanding devices during the Run Test/Idle, Pause-DR, or Pause-IR states, enabling the selection and operation of devices through innovative TAP state transition sequences and circuitry, such as the Addressable and Commandable TAP (ATAP) configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If unique TMS or TCK signals are used for each device to enable addressing and commanding, then device access functionality is improved, but wiring complexity increases
Solution Approach 1:
The TMS and TCK signals are designed to serve multiple devices simultaneously through a shared bus structure. The control bit mechanism enables a single TMS and TCK signal to address and command multiple devices in different states, eliminating the need for unique signals per device while maintaining full functionality.
Solution Approach 2:
The addressing mechanism segments device selection by utilizing the state machine's different operational states (Run Test/Idle, Pause-DR, Pause-IR). Each device can be selectively addressed by controlling which state transitions occur, allowing multiple devices to share the same physical interface without signal conflict.
2Device complexity
If the TAP operates only in Run Test/Idle state for addressing, then state machine simplicity is maintained, but operational versatility is limited
Solution Approach 1:
The TAP state machine is enhanced with dynamic state utilization, where different states (Run Test/Idle, Pause-DR, Pause-IR) serve different functional purposes in the addressing and commanding sequence. This allows the same state machine structure to provide versatile operational capabilities by strategically using its existing states for multiple purposes.
Solution Approach 2:
The system prepares for device addressing by transitioning to appropriate pause states before actual addressing occurs. This preliminary positioning in specific states enables subsequent addressing operations to proceed efficiently without requiring additional complex state transitions.
3Stability of the object's composition
If address and command input is limited to specific states only, then signal stability is improved, but access efficiency decreases
Solution Approach 1:
The addressing and commanding operations can proceed continuously through multiple state transitions without requiring the system to return to a base state between operations. The control bit mechanism enables seamless progression through state transitions while maintaining stable signal levels, improving access efficiency without sacrificing signal integrity.
Data Source
AI summary
The disclosure provides a novel method and apparatus for inputting addresses to devices to select the device TAP for access. Further, the disclosure provides a novel method and apparatus for inputting addresses for selecting device TAPs and for inputting commands for commanding circuitry within the device. The inputting of addresses or the inputting of addresses and commands is initiated by a control bit input on TDI that is recognized during the Run Test/Idle, Pause-DR or Pause-IR TAP states.