Transmission Frame CRC Generation Using Differential Bit Regions
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Solution Overview
Problem
In fields requiring functional safety communication, the existing methods for calculating CRC (Cyclic Redundancy Check) either increase computation time when the difference between data sets is large or require excessive storage for small differences, making it challenging to balance execution time and table size.
Innovation Solution
A data processing device that logically divides a transmission frame into regions with regular, semi-fixed, and non-regular bit strings, using a CRC table to store only the CRCs for regular and defined bit strings, and a differential CRC for differences, allowing for efficient generation of the transmission frame CRC through exclusive OR operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If all CRCs corresponding to differences between the first data and the second data are retained in a table, then the number of times of table reference is small, but the size of the table is enormous and many storage regions are required
Solution Approach 1:
The patent segments the transmission frame into multiple regions (first region with regular bit string, second region with similar bit string, third region with non-regular bit string) and calculates CRC for each region separately. This segmentation allows the system to use a smaller CRC table while reducing computation time by processing only specific regions rather than the entire frame.
Solution Approach 2:
The patent applies different processing strategies to different regions of the transmission frame. The first region uses a pre-calculated CRC from the table, the second region uses XOR operation with a differential CRC, and the third region undergoes full CRC calculation. This local differentiation optimizes both computation speed and table size requirements.
2Quantity of substance
If the difference between the first data and the second data is obtained for each bit to obtain a CRC of the second data, then the size of the table retaining CRCs is relatively small, but the number of times of table reference is increased and the CRC computation time is increased
Solution Approach 1:
The patent pre-calculates and stores differential CRCs in the table corresponding to various bit differences. When processing the second region, the system can directly reference these pre-computed differential CRCs and perform a single XOR operation, rather than calculating CRC bit-by-bit. This preliminary preparation significantly reduces computation time while keeping the table size manageable.
3Loss of time
In fields requiring functional safety communication, if the CRC computation time is desired to be shortened, then the worst-case execution time has to be considered, but existing methods cannot sufficiently shorten the computation time without increasing table size
Solution Approach 1:
The patent dynamically selects which regions to process based on their characteristics. Regular regions are handled via table lookup, similar regions via differential XOR, and non-regular regions via full calculation. This dynamic approach optimizes computation time for functional safety applications while adapting storage requirements to actual data patterns, avoiding unnecessary table expansions.
Data Source
AI summary
A region specifying unit specifies a first region where a regular bit string is in a transmission frame, a second region which has a bit string similar to a defined bit string, and a third region which has a non-regular bit string and extracts a difference between the bit string in the second region and the defined bit string. A first CRC acquisition unit acquires a first CRC corresponding to the regular bit string. A second CRC acquisition unit acquires a second CRC corresponding to the defined bit string. A differential CRC acquisition unit acquires a differential CRC corresponding to the extracted difference. A third CRC generation unit generates a third CRC corresponding to a bit string in the third region. A frame CRC generation unit generates a CRC of the transmission frame using the first CRC, the second CRC, the differential CRC, and the third CRC.