Serial Bus Error Signaling via ACK NACK Time Windows
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The asymmetrical deformation of bits on the CAN bus due to varying drive levels limits the bit rate for serial transmission and makes error signaling unreliable, as recessive bits become shorter and harder to identify at higher rates, and error identifiers may not be reliably identifiable.
Innovation Solution
A user station for a serial bus system that includes a communication control unit and a transceiver device, which provides ACK and NACK time windows for error signaling without driving a level on the bus line during these windows, allowing for symmetric bit transmission and reducing the sender's effort in identifying errors, thereby increasing bit rates and ensuring reliable error signaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If asymmetrical bus levels are used for error signaling in CAN protocol, then error identification is possible, but bit rate is limited due to asymmetric bit deformation
Solution Approach 1:
The patent extracts the error signaling function from the data transmission phase by introducing separate ACK and NACK time windows. During these windows, the sender explicitly refrains from driving bus levels, allowing receivers to indicate errors without interference from asymmetrical bit deformation that occurs during normal data transmission.
Solution Approach 2:
The sender prepares the bus by entering a high-impedance state in advance of the ACK/NACK time windows, ensuring that the bus is ready to receive error signals without distortion. This preliminary action of disabling the driver before error signaling occurs prevents the asymmetrical deformation problem.
2Productivity
If higher bit rates are used for serial transmission, then productivity increases, but recessive bits become shorter and harder to identify
Solution Approach 1:
The patent introduces periodic ACK and NACK time windows within the message structure where error signaling occurs. These periodic intervals are specifically designed with sufficient duration to allow reliable identification of error signals even at high bit rates, separating the error signaling function from the continuous data transmission.
3Productivity
If the sender continuously drives bus levels during message transmission, then data transmission is efficient, but error signaling becomes unreliable
Solution Approach 1:
The patent segments the message transmission into distinct phases: data transmission phases where the sender drives the bus efficiently, and separate ACK/NACK time windows where the sender refrains from driving to allow reliable error signaling. This temporal segmentation resolves the contradiction by assigning different functions to different time segments.
Data Source
AI summary
A user station for a serial bus system and a method for error signaling for a message received in a serial bus system are provided. The user station includes a communication control unit for creating a message to be transmitted serially to at least one further user station of the bus system, or for reading a message, received serially from at least one further user station, and a transceiver device for transmitting the created message on a bus line or for receiving a message from the bus line, the communication control unit and/or the transceiver device provide an ACK time window for an ACK signal and/or a NACK time window for a NACK signal in the message to be transmitted for a signaling of whether or not at least one further user station has identified an error in the transmitted message.