Multi-Wire Bus Skew Calibration Using Composite Comparator Signals
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Solution Overview
Problem
In high-speed chip-to-chip communication systems, differential signal arrival times across multiple wires cause skew, leading to improper reception and decoding of vector signaling codes, which existing technologies struggle to accurately measure and correct.
Innovation Solution
The system employs multi-input comparators to generate skew measurement signals by forming linear combinations of received symbols, updating clock phase error counts, and adjusting wire-specific delay values based on these measurements to compensate for skew, ensuring accurate sampling and decoding of vector signaling codes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-wire interfaces are used for high-speed chip-to-chip communication, then bandwidth is increased, but skew between wires causes improper reception and decoding
Solution Approach 1:
The system performs preliminary skew measurement and correction before decoding operations. A skew measurement unit measures the skew between multiple wires, and delay adjustment units adjust the timing of signals on each wire to compensate for skew, ensuring all signals arrive simultaneously at the decoder input, thereby preventing decoding errors
Solution Approach 2:
The system implements a feedback mechanism where skew measurement results are continuously monitored and used to dynamically adjust delay values. The skew measurement unit provides real-time skew information to delay adjustment units, which modify their delay parameters accordingly, creating a closed-loop control system that maintains synchronization despite environmental variations
2Measurement precision
If skew correction is implemented, then reception accuracy is improved, but measurement and correction complexity increases
Solution Approach 1:
The skew correction system is segmented into independent functional units: a skew measurement unit that measures skew for each wire pair, and individual delay adjustment units for each wire. This modular segmentation allows each unit to operate independently with simple logic, reducing overall system complexity while achieving precise skew correction through coordinated operation of multiple simple units
Solution Approach 2:
The patent introduces a dedicated skew measurement unit as an intermediary component that bridges the gap between signal transmission and decoding. This intermediary unit simplifies the complexity by centralizing the measurement function and providing standardized skew information to delay adjustment units, rather than requiring complex interconnections between multiple adjustment units
Data Source
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AI summary
Methods and systems are described for receiving, over a plurality of consecutive signaling intervals, a plurality of codewords, each codeword received as a plurality of symbols via wires of a multi-wire bus, the plurality of symbols received at a plurality of multi-input comparators (MICs), wherein each symbol is received by at least two MICs, generating, for each codeword, a corresponding linear combination of the received symbols, generating a plurality of composite skew measurement signals over the plurality of consecutive signaling intervals, each composite skew measurement signal based on samples of one or more linear combinations, and updating wire-specific skew values of the wires of the multi-wire bus, wherein one or more wire-specific skew values are updated according to composite skew measurement signals associated with linear combinations formed by at least two different MICs.