CAN FD Light Three-State Driver for Shared Bus Communication
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Solution Overview
Problem
The high cost and complexity of providing a CAN FD transceiver for each processing unit in a system, especially in applications where multiple processing units need to communicate on a CAN FD Light bus, pose a significant challenge in managing communication effectively.
Innovation Solution
A processing system with a CAN FD Light controller that includes a three-state driver circuit and combinational logic to manage signal levels, allowing for the transmission and reception of CAN FD Light frames without the need for a separate transceiver for each processing unit, by using a shared transmission line and pull-up resistance to implement a push-pull configuration for higher transmission speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a CAN FD transceiver is provided for each processing unit, then communication reliability is improved, but system cost and complexity increase
Solution Approach 1:
Multiple processing units share a common CAN FD transceiver through a bus structure. The transceiver is shared among several processing units via a communication bus, eliminating the need for individual transceivers at each unit while maintaining communication functionality. This merging approach reduces component count and system complexity while preserving reliable CAN FD communication.
Solution Approach 2:
A single CAN FD transceiver serves multiple processing units simultaneously. The transceiver is designed to handle communications for several processing units through protocol management and signal routing, making one device perform the function of what would traditionally require multiple dedicated transceivers.
2Device complexity
If a shared transmission line is used without individual transceivers, then cost and complexity are reduced, but transmission speed decreases
Solution Approach 1:
The system dynamically switches between push-pull and high-impedance states based on communication needs. During active transmission, the output driver operates in push-pull mode for high-speed data transfer. When not transmitting, it switches to high-impedance state to allow other units to communicate. This dynamic switching enables the shared bus to achieve speeds comparable to dedicated transceivers.
Solution Approach 2:
The shared transmission line operates in periodic time-division multiplexing mode where different processing units take turns transmitting data. Each unit has designated time slots for communication, and the output driver alternates between active driving states and high-impedance states accordingly. This periodic operation allows multiple units to share the transmission medium while maintaining acceptable data rates.
Data Source
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AI summary
A processing system (10a) is described. The processing system comprises a three-state driver circuit (502) and a CAN FD Light controller (500). The CAN FD Light controller (500) is configured to sequentially transmit the bits of a CAN FD Light frame, wherein the CAN FD Light frame comprises a start-of-frame bit (SOF), a sequence of bits (CD-EOF) comprising in sequence a Cyclic Redundancy Check, CRC, delimiter bit (CD), an acknowledge bit (AS), an acknowledge delimiter bit (AD) and an End-of-Frame field (EOF) having 7 bits, and a plurality of intermediate bits (SID-CRC) between said start-of-frame bit (SOF) and said CRC delimiter bit (CD). In particular, the CAN FD Light controller (500) is configured to sequentially transmit the bits of the CAN FD Light frame via the three-state driver circuit (502) by using a push-pull configuration (CTRL1) when transmitting the start-of-frame bit (SOF) and the intermediate bits (SID-CRC). However, once having transmitted the intermediate bits (SID-CRC), the CAN FD Light controller (500) activates a high-impedance state (CTRL1) of the three-state driver circuit (502).