4B5B NRZI Coding for Clock Extraction and Command Reliability
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Solution Overview
Problem
Current data communication technologies face challenges in efficiently managing consecutive data values, limiting command codes, and ensuring high reliability and speed, especially in high-frequency communication networks, where clock extraction and error detection in control information are critical.
Innovation Solution
The proposed solution involves a coding apparatus and method that converts 4-bit data into 5-bit patterns and 5N-bit command patterns using NRZI coding, allowing for flexible command code setting, efficient data frame identification, and error detection in both data and control information portions, while maintaining high communication speed and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If Manchester code is used for clock extraction, then clock extraction becomes easier, but the required bandwidth doubles
Solution Approach 1:
The patent changes the encoding parameters by using 4B5B conversion to transform 4-bit data into 5-bit patterns with controlled transition characteristics, then applies NRZI coding to achieve clock extraction without doubling bandwidth. This modifies the original data representation parameters to balance clock extraction ease with bandwidth efficiency.
2Ease of operation
If 4B5B conversion with NRZI coding is used, then clock extraction is facilitated, but the maximum bit length undergoing no edge increases to 4
Solution Approach 1:
The patent applies local quality by imposing specific constraints on the 5-bit data patterns generated through 4B5B conversion, ensuring that head end two bits and tail end two bits follow particular patterns. This local control of bit patterns reduces the maximum consecutive zero length to 3, thereby limiting the maximum bit length undergoing no edge while maintaining clock extraction capability.
3Reliability
If command codes are assigned individually to each pattern, then communication reliability is maintained, but the number of usable commands is limited
Solution Approach 1:
The patent implements universality by introducing a command code field that can be combined with data patterns to create multiple command classifications. Instead of assigning one command per pattern, the system uses a universal command code structure that can identify different command types, thereby expanding the number of usable commands while maintaining communication reliability through proper error detection mechanisms.
4Measurement precision
If longer lengthened identifier is assigned to longer lengthened data frame, then frame identification accuracy is improved, but communication efficiency decreases when communication frequency of longer frames is higher
Solution Approach 1:
The patent applies dynamics by making the identifier length adaptive rather than fixed. The system dynamically adjusts identifier length based on the communication frequency and characteristics of different frame types. When longer frames are transmitted at higher frequencies, the system optimizes identifier length to balance identification accuracy with communication efficiency, preventing unnecessary overhead from excessive identifier lengths.
Data Source
AI summary
A 4B5B encoder converts an inputted 4-bit data into a pattern of a 5-bit data in which (i) the number of bits of consecutive “0” data values is permitted to be maximum two, and, simultaneously, (ii) maximum one bit of head end two bits is permitted to have a “0” data value and maximum one bit of tail end two bits is permitted to have a “0” data value. A 5N-bit command encoder converts a command into a command pattern in which the number of bits contained in consecutive “0” data values is permitted to be maximum two. The data after the conversion and the command after the conversion are converted into NRZI codes by an NRZI encoder.