Content-Terminated DMA Circuit for Autonomous Data Transfer
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Solution Overview
Problem
Conventional Direct Memory Access (DMA) controllers are unable to terminate data transfers of unknown length without processor intervention, leading to processor-intensive tasks and performance degradation, especially when dealing with non-cacheable memory accesses.
Innovation Solution
A Content-Terminated Direct Memory Access (CT-DMA) circuit that reads and writes data until filter criteria, including pattern data and termination rules, are met, allowing autonomous termination of data transfers without processor involvement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional DMA controller is used to transfer data of unknown length, then the processor must manually read and compare characters to determine string length, but this causes the processor to spend considerable time waiting for memory operations and severely degrades processor performance
Solution Approach 1:
The DMA controller is enhanced with content-terminated transfer capability, allowing it to autonomously determine when to stop transferring data by detecting termination patterns (such as null characters) without requiring continuous processor intervention. The DMA controller reads data, compares it against termination criteria, and automatically terminates the transfer when the pattern is detected, making the system self-managing rather than processor-dependent
Solution Approach 2:
The patent introduces an intermediary comparison mechanism within the DMA controller that handles the character comparison task. Instead of the processor directly comparing characters to determine string length, the DMA controller performs this comparison function as an intermediary step, freeing the processor from the tedious manual comparison process while maintaining accurate length determination
2Measurement precision
If the processor manually compares each character to determine string length, then accurate length determination is achieved, but the processor performs a very large number of memory accesses and the task becomes processor-intensive
Solution Approach 1:
The DMA controller performs the string length determination task autonomously by continuously comparing transferred data against termination patterns. The controller manages its own comparison operations and termination decisions without requiring the processor to perform numerous manual comparison cycles, thereby reducing processor task complexity while maintaining accurate length measurement
Solution Approach 2:
The patent merges the data transfer function with the length determination function into a single integrated DMA operation. Instead of separating the transfer process from the comparison process, the enhanced DMA controller combines both functions, performing data transfer and termination pattern detection simultaneously in one coordinated operation
3Ease of operation
If conventional DMA controllers are used, then simple data transfer is achieved, but they cannot inspect the data they transfer and must blindly transfer a specified amount of data
Solution Approach 1:
The DMA controller is enhanced to perform multiple functions: it not only transfers data blindly as before but also inspects the transferred data for termination patterns and automatically determines when to stop. This multi-functional capability allows the same hardware to handle both simple specified-length transfers and content-terminated transfers of unknown length, increasing adaptability without sacrificing operational simplicity
Data Source
AI summary
A Content-Terminated Direct Memory Access (CT-DMA) circuit autonomously transfers data of an unknown length from a source to a destination, terminating the transfer based on the content of the data. Filter criteria are provided to the CT-DMA prior to the data transfer. The filter criteria include pattern data that are compared to transfer data, and transfer termination rules for interpreting the comparison results. Data are written to the destination until the filter criteria are met. Representative filter criteria may include that one or more units of transfer data match pattern data; that one or more units of transfer data fail to match pattern data; or that one or more units of transfer data match pattern data a predetermined number of times.