ISO 20794-4-2020 PDF

Full title and description

ISO 20794-4:2020 — Road vehicles — Clock extension peripheral interface (CXPI) — Part 4: Data link layer and physical layer. This part of ISO 20794 specifies the CXPI data link layer (DLL) behavior and the CXPI physical layer (PHY) requirements for in-vehicle CXPI networks, including signalling, encoding/decoding, collision resolution and physical media requirements.

Abstract

This document defines the CXPI data link layer and the CXPI physical layer. The DLL is based on priority-based network access, non-destructive content-based arbitration, broadcast frame transfer with acceptance filtering, and node-related error detection and signalling. The PHY requirements are split into sub-layers: physical signalling (PS), physical media attachment (PMA), physical media dependent (PMD) and physical media (PM).

General information

• Status: Published (International Standard, confirmed).
• Publication date: February 2020 (2020-02).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 43.040.15 (Road vehicles — vehicle electronics/communication).
• Edition / version: Edition 1 (2020).
• Number of pages: 56 pages.

Source details and summary information above are taken from the ISO bibliographic record for ISO 20794-4:2020.

Scope

ISO 20794-4:2020 specifies the services, protocols and electrical/physical characteristics required to implement the CXPI data link layer and physical layer in road-vehicle electronic networks. It defines frame formats, arbitration and access rules, error detection and signalling behavior, and the physical signalling, waveform shaping, termination/protection requirements and connector/cabling considerations for CXPI networks used in vehicle subsystems. The standard is intended to enable interoperable CXPI nodes (commanders and responders) and to provide a basis for conformance testing.

Key topics and requirements

• Priority-based CXPI network access and non-destructive content-based arbitration.
• Frame format, broadcast transfer, acceptance filtering and node-related error detection/signalling.
• Physical signalling sub-layer (clock generation, encoding/decoding, bit-wise collision resolution).
• Physical media attachment (PMA) requirements for signal shaping and waveform logic.
• Physical media dependent (PMD) requirements including network termination and ESD protection.
• Physical media (PM) requirements covering cable/wiring harness and connector considerations.
• Normative requirements intended to support conformance testing and interoperable CXPI device design.

Typical use and users

Typical users include automotive system and ECU designers, embedded firmware and hardware engineers implementing CXPI transceivers, automotive component suppliers, test and validation laboratories, and integrators responsible for in-vehicle low-speed serial networks. The standard is used when designing CXPI physical interfaces, data-link implementations and when establishing conformance and interoperability test plans for CXPI devices.

Related standards

ISO 20794 is a multipart series covering CXPI layers and conformance test plans. Relevant parts in the series include ISO 20794-2 (Application layer), ISO 20794-3 (Transport and network layer), ISO 20794-5 (Application layer conformance test plan), ISO 20794-6 (Transport and network layer conformance test plan) and other conformance parts that together define the full CXPI protocol stack and testability requirements.

Keywords

CXPI, clock extension peripheral interface, data link layer, physical layer, PHY, PMA, PMD, physical media, automotive network, ECU communication, conformance testing.

FAQ

Q: What is this standard?

A: ISO 20794-4:2020 is the part of the ISO 20794 series that defines the CXPI data link layer and physical layer requirements for road-vehicle networks, specifying frame and signaling behaviour as well as physical interface and wiring requirements.

Q: What does it cover?

A: It covers data-link services and protocols (arbitration, frame transfer, error handling) and the physical layer split into PS, PMA, PMD and PM — including clock generation, encoding/decoding, collision resolution, waveform shaping, termination, protection and connector/wiring requirements.

Q: Who typically uses it?

A: Automotive electronics designers, ECU and transceiver IC manufacturers, system integrators, and conformance/test labs use this standard when implementing or validating CXPI-based subsystems.

Q: Is it current or superseded?

A: ISO 20794-4:2020 was published in February 2020 and is recorded as a published (confirmed) international standard; ISO standards are normally reviewed on a five-year cycle for confirmation or revision.

Q: Is it part of a series?

A: Yes. ISO 20794 is a multipart series addressing CXPI protocol layers and conformance test plans (examples: Part 2 — Application layer; Part 3 — Transport and network layer; Parts 5–7 — conformance test plans for the different layers).

Q: What are the key keywords?

A: CXPI, data link layer, physical layer, physical signalling, PMA, PMD, arbitration, frame format, automotive network, conformance testing.