Interconnect Symbol Encoding Using MRU Values to Cut PAM Overhead
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Solution Overview
Problem
Existing PAM-based interconnects face challenges with high power consumption and signal integrity issues due to increased power usage and susceptibility to crosstalk errors, particularly with PAM-4 and PAM-8 signaling, which require auxiliary bits for encoding and decoding, leading to increased resource costs and encoding overhead.
Innovation Solution
Implementing a deterministic counter-based mechanism for symbol training that reduces the need for auxiliary bits by using most recently used (MRU) symbols to encode and decode data, thereby reducing symbol transitions and improving signal integrity, while conserving power and bandwidth by employing XOR or XNOR operations based on MRU values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If PAM-4 or PAM-8 signaling is used to increase bandwidth, then data transfer capacity is improved, but power consumption increases and signal integrity deteriorates
Solution Approach 1:
The patent changes the encoding parameters by using deterministic counter-based encoding that tracks symbol frequencies and selects codewords with minimal transitions. This parameter change reduces the number of signal transitions required for data transmission, thereby reducing power consumption while maintaining high data transfer capacity through PAM-4 or PAM-8 signaling
2Productivity
If PAM-4 or PAM-8 signaling is used to increase bandwidth, then data transfer capacity is improved, but signal integrity deteriorates due to crosstalk errors
Solution Approach 1:
The patent changes the encoding strategy to use deterministic counter-based encoding that minimizes symbol transitions. By selecting codewords that require fewer transitions between symbol states, the signal remains more stable and less susceptible to crosstalk errors, thereby improving signal integrity while maintaining high data transfer capacity
3Reliability
If auxiliary bits are used for encoding and decoding in PAM-based interconnects, then signal integrity is improved, but device complexity and resource costs increase
Solution Approach 1:
The patent extracts and eliminates the need for auxiliary bits by using deterministic counter-based encoding. The encoder and decoder both maintain identical counter states that track symbol frequencies, allowing the decoder to automatically determine the correct codeword interpretation without requiring additional auxiliary bits. This removes the encoding overhead while maintaining signal integrity through the deterministic encoding process
Data Source
AI summary
Data are serially communicated over an interconnect between an encoder and a decoder. The encoder includes a first training unit to count a frequency of symbol values in symbol blocks of a set of N number of symbol blocks in an epoch. A circular shift unit of the encoder stores a set of most-recently-used (MRU) amplitude values. An XOR unit is coupled to the first training unit and the first circular shift unit as inputs and to the interconnect as output. A transmitter is coupled to the encoder XOR unit and the interconnect and thereby contemporaneously sends symbols and trains on the symbols. In a system, a device includes a receiver and decoder that receive, from the encoder, symbols over the interconnect. The decoder includes its own training unit for decoding the transmitted symbols.