Ethernet Controller Direct Memory Access for Vehicle Data Exchange
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Solution Overview
Problem
In vehicle electrical systems, the use of descriptor-based communication systems like Ethernet can lead to bottlenecks in data exchange due to the involvement of the CPU in processing messages, which is problematic in systems with strict real-time requirements, especially when there are powerful vehicle central computers and less powerful zone control units.
Innovation Solution
Implementing a method where one user can directly write or read arbitrary data areas in another user via DMA, using descriptors independently of the bus system, allowing the Ethernet controller to access buffers without CPU involvement, enabling fully automated communication and reducing the need for CPU processing in data exchange.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If CPU is involved in processing messages in descriptor-based communication systems, then data exchange can be performed with flexible control, but processing time and latency increase
Solution Approach 1:
The patent extracts the CPU from the message processing path by implementing direct memory access (DMA) between Ethernet controllers and memory. The CPU is removed from the critical data exchange path, allowing Ethernet controllers to read/write messages directly to memory buffers without CPU intervention, thereby reducing processing time while maintaining system control flexibility.
Solution Approach 2:
The patent implements self-service communication where Ethernet controllers autonomously handle message transmission and reception by directly accessing memory buffers. The controllers can independently read transmit descriptors, write messages to memory, read received messages, and update receive descriptors without requiring CPU involvement, enabling the communication subsystem to serve itself.
2Adaptability or versatility
If descriptor-based communication is used in Ethernet systems, then data exchange flexibility is improved, but bottlenecks occur in real-time data exchange
Solution Approach 1:
The patent segments the communication system into independent functional units: Ethernet controllers, memory buffers, and descriptor structures. Each Ethernet controller has dedicated memory buffers and transmit/receive descriptors, allowing parallel operation of multiple communication channels without interfering with each other, thus improving real-time data exchange capacity while maintaining flexibility.
Solution Approach 2:
The patent introduces descriptors as intermediary data structures that bridge the CPU and Ethernet controllers. Transmit descriptors contain message length and buffer address information, enabling Ethernet controllers to autonomously access memory. This intermediary mechanism allows flexible descriptor-based communication while eliminating CPU bottlenecks in real-time data exchange.
3Loss of time
If direct memory access is implemented for Ethernet controllers, then processing time is reduced, but system complexity increases
Solution Approach 1:
The patent uses descriptor copying where transmit descriptors and receive descriptors are replicated in memory for each Ethernet controller. These descriptor copies contain all necessary information (message length, buffer addresses) for autonomous memory access. This copying approach enables direct memory access functionality while keeping the base Ethernet controller design relatively simple.
Data Source
AI summary
A method for operating a communications network that includes at least two users that are communicatively connected to one another via a descriptor-based communication system such as Ethernet. For writing data from a writing user into a user to be written, receive descriptors and data are transmitted from the writing user to the user to be written, in the user to be written, the data being written according to the received receive descriptors, and/or for reading data by a reading user from a user to be read, transmit descriptors are transmitted from the reading user to the user to be read, data being read by the user to be read according to the received transmit descriptors and transmitted to the reading user. A communications network and users are also described.