Serial Interface Power Control via RTS CTS Lines
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Solution Overview
Problem
Existing serial communication interfaces face challenges in efficiently managing low-power states without additional signal lines, leading to increased power consumption and reduced data transmission rates when not actively communicating.
Innovation Solution
A method utilizing standard flow-control signal lines (RTS/CTS) to control the low-power states of serial interfaces, enabling wake-up and transmission authorization through these lines, and incorporating an end-of-transmission flag to optimize message handling and minimize power state transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional signal lines are provided for wake-up functionality, then the ability to wake up from low-power state is improved, but the device complexity and power consumption increase
Solution Approach 1:
The patent applies multi-functionality by enabling flow-control signal lines (RTS/CTS) to serve dual purposes: their traditional flow-control function and an additional wake-up function. When the receiver needs to wake up the transmitter from low-power state, it activates the CTS line, which the transmitter interprets as a wake-up signal. This eliminates the need for dedicated wake-up signal lines while maintaining reliable wake-up capability.
2Productivity
If interfaces remain in live state during idle periods, then communication responsiveness is improved, but power consumption increases
Solution Approach 1:
The patent implements periodic action by allowing interfaces to alternate between live and low-power states based on communication activity. When no communication is needed, interfaces transition to low-power state to conserve energy. When communication is required, they wake up to live state. The flow-control lines enable this periodic transition while maintaining the ability to respond quickly when needed.
3Device complexity
If flow-control lines are used for wake-up signaling, then device complexity is reduced, but the precision of flow-control signaling may be affected
Solution Approach 1:
The patent uses feedback mechanisms to resolve signal interpretation ambiguity. The transmitter monitors the CTS line not only for flow-control feedback but also for wake-up requests. The receiver provides clear feedback by activating CTS only when it needs to wake up the transmitter, and the transmitter responds by transitioning from low-power state. This feedback loop ensures precise signal interpretation despite the dual-use of the line.
Data Source
AI summary
A method for controlling a low-power state of a pair of serial interfaces using a pair of flow-control signal lines may include enabling a first of the flow-control lines by a first one of the interfaces for signaling a transmission request to the second interface. The method may also include, in response to the transmission request, waking up to a live state from a low-power state and enabling a second flow-control line for signaling a transmission authorization to the first interface. In response to the transmission authorization, the method may include initiating a transmission of a message to the second interface, and upon reaching an offset before the end of the message transmission, disabling the first flow-control line by the first interface. The method may also include, at the end of the message transmission, disabling the second flow-control line and going back into the low-power state.