Chip-to-Chip Bus Encoding for Common-Mode and SSO Noise Rejection
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Solution Overview
Problem
Current communication bus technologies face limitations in pin efficiency and noise resilience, particularly in high-speed applications where the number of wires is not a power of two, and existing methods like Orthogonal Differential Vector Signaling (ODVS) and Coded Differential Vector Signaling (COVECS) may require complex circuitry and compromise pin efficiency for noise resilience.
Innovation Solution
The use of spherical codes, specifically sparse permutation modulation codes, which map information bits to a codeword represented as a vector of components, allowing for efficient encoding and decoding while achieving improved noise resilience and pin efficiency by transmitting signals over multiple wires, where each component can have multiple values, thereby optimizing tradeoffs between pin efficiency and noise resilience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the number of wires in the communication bus is increased to achieve higher communication speed, then the communication speed is improved, but the number of pins required increases which reduces pin efficiency
Solution Approach 1:
The patent changes the signaling parameters by using multi-level voltage signals (more than two signal levels) instead of traditional binary signaling. This allows more bits to be transmitted per wire per clock cycle, improving communication speed without proportionally increasing the number of pins. The encoding schemes transform binary data into multi-level signals that can be transmitted over the same physical infrastructure with higher efficiency.
2Power
If transmit power is increased to improve communication performance, then signal strength is improved, but noise and interference increase which lowers performance
Solution Approach 1:
The patent converts the harmful effect of noise into a beneficial feature by using differential signaling and common-mode rejection techniques. The system is designed to reject common-mode noise that affects all wires equally, transforming the universal interference into a cancelable artifact. Additionally, the multi-level signaling schemes are designed with noise margins that allow reliable detection even in the presence of interference.
Solution Approach 2:
The patent employs composite signaling approaches that combine multiple techniques: differential signaling, multi-level voltage encoding, and error correction codes. This composite approach creates a robust communication system that maintains performance without requiring excessive transmit power, as each layer of the composite solution contributes to noise rejection and signal integrity.
3Device complexity
If single-ended signaling is used to reduce the number of wires, then wire count is reduced, but the system becomes susceptible to common-mode noise and SSO noise
Solution Approach 1:
The patent segments the signaling approach by using separate differential pairs for different signal purposes and implementing segmented encoding schemes. Instead of using a single-ended bus for all communications, the system divides the communication channels into multiple differential segments, each with its own noise rejection capabilities. This segmentation allows the system to maintain low wire count while achieving noise immunity through the distributed differential structure.
4Object-affected harmful factors
If differential signaling is used to reject common-mode noise, then noise resilience is improved, but the number of pins required doubles compared to single-ended signaling
Solution Approach 1:
The patent merges multiple differential signaling channels into a unified multi-level signaling system. Instead of treating each differential pair as an independent binary channel, the system combines them to create multi-level signals that transmit more information per pin. This merging allows the system to achieve both noise resilience through differential signaling and pin efficiency through information densification across the combined channels.
5Object-affected harmful factors
If existing methods like ODVS or COVECS are used to achieve noise resilience, then common-mode noise rejection is improved, but pin efficiency is compromised and circuit complexity increases
Solution Approach 1:
The patent implements self-service encoding and decoding algorithms that automatically optimize the signaling without requiring complex external control circuitry. The encoding schemes are designed to inherently provide noise resilience and error correction, allowing the system to serve its own noise rejection needs without additional complex hardware. The multi-level signaling automatically adapts to channel conditions through the properties of the encoding itself rather than requiring complex adaptive circuitry.
Data Source
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AI summary
Method and apparatus for obtaining a sequence of bits comprising a set of n bits (1510), and responsively forming an index t representing a binary expansion of the set of n bits (1520), wherein n is an integer greater than one and wherein 0<= t <= 2^n-1, generating an output vector v having a length 2^n by setting a position v[t] of the output vector to a value -(2^n)+1 and setting all other positions of the output vector v to a value of '1' (1530), and outputting the output vector v (1540) for transmission over a multi-wire bus.