Bi-Directional Bus Repeater Timing Logic for Lockup-Free Switching
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Solution Overview
Problem
Bi-directional communication systems with bi-directional bus repeaters suffer from a self-locking problem due to simultaneous high-to-low transitions at input terminals, leading to communication bus lockup.
Innovation Solution
The bi-directional bus repeater design includes pulldown controllers that activate only after detecting a high-to-low transition and a logical high at their respective input terminals, with time delays preventing simultaneous activation, thereby avoiding self-locking. This design ensures that the first and second pulldown elements are activated independently of each other, even during simultaneous transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If pull-down transistors are activated immediately upon high-to-low transition at input terminals, then response speed is improved, but self-locking occurs causing communication bus lockup
Solution Approach 1:
The patent applies preliminary action by requiring the pulldown controller to detect the logical high state at the first input terminal before activating the pull-down transistor in response to a high-to-low transition at the second input terminal. This preparatory detection ensures the controller is ready to act only when appropriate conditions are met, preventing premature activation that would cause self-locking while maintaining fast response when valid transitions occur.
Solution Approach 2:
The patent implements feedback by having the pulldown controller continuously monitor the state of the first input terminal and use this information to control activation of the pull-down transistor. The controller only activates the transistor when it detects both a high-to-low transition at the second input and a logical high at the first input, creating a feedback mechanism that prevents self-locking by ensuring proper signal conditions exist before allowing pull-down action.
2Reliability
If simultaneous high-to-low transitions are detected at both input terminals, then communication robustness is improved, but both pulldown elements activate causing self-locking
Solution Approach 1:
The patent applies asymmetry by creating an asymmetric control relationship between the two input terminals. The pulldown controller at each end of the bus requires detection of a logical high at its local input terminal before responding to transitions at the remote input terminal. This asymmetric requirement breaks the symmetry of simultaneous activation that causes self-locking, allowing the system to handle simultaneous transitions robustly without both pulldown elements activating.
3Productivity
If pulldown elements are activated without input state verification, then activation speed is improved, but communication bus lockup occurs
Solution Approach 1:
The patent applies preliminary action by requiring the pulldown controller to verify the logical high state at the first input terminal before activating the pull-down transistor. This preliminary verification step ensures that activation only occurs when proper signal conditions are present, maintaining fast activation speed when valid while preventing bus lockup through conditional activation based on input state verification.
Data Source
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AI summary
The present invention relates to a bi-directional bus repeater. The present invention further relates to a communication bus comprising such bi-directional bus repeater, and to a communication system comprising such communication bus. According to the present invention, the bi-directional bus repeater comprises a first input terminal, a second input terminal, a first pulldown element connected to the first input terminal, and a second pulldown element connected to the second input terminal. By ensuring that the activation of the first and second pulldown elements is dependent on the state of the corresponding input terminal and the detection of a high-to-low transition of the corresponding other input terminal, the problem of self-locking can be avoided or at least minimized.