ISO 20794-3-2020 PDF

Full title and description

Road vehicles — Clock extension peripheral interface (CXPI) — Part 3: Transport and network layer. This part of ISO 20794 specifies the OSI transport and network layers for the CXPI in-vehicle communication protocol, describing services and protocols used primarily for diagnostic communication and node configuration in automotive systems.

Abstract

ISO 20794-3:2020 defines the transport layer and network layer for CXPI. The transport layer transforms messages into single packets, adds protocol control information and packet identifiers (used for diagnostics and node configuration) and performs transport-level error detection. The network layer adds node addressing and timing for diagnostic/node-configuration segments and is used to map service interface parameters between lower and upper OSI layers rather than for normal regular communication.

General information

• Status: Published (confirmed).
• Publication date: 2020-02 (February 2020).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 43.040.15 (Car informatics; on-board computer systems).
• Edition / version: Edition 1 (2020-02).
• Number of pages: 23 pages.

Scope

Specifies the CXPI transport and network layers by means of defined services and protocols applicable to diagnostic communication and node configuration. The document details how the transport layer packages messages, appends control and identification information and performs error detection, and how the network layer provides node addressing and timing for segments used in diagnostics/configuration. Both layers are presented primarily as mapping interfaces between lower and upper OSI layers rather than for routine application-level message transfer.

Key topics and requirements

• Definition of transport-layer services: message-to-packet transformation, protocol control information, packet identifiers, and transport error detection.
• Definition of network-layer services: node addressing for diagnostic/configuration segments and timing/segment handling rules.
• Clarification that transport and network layers are chiefly used for diagnostic and node-configuration mapping between OSI layers, not for normal application communication.
• Interoperation expectations with other CXPI layers (application, data link, physical) as specified in the multi-part ISO 20794 series.
• Conformance and test-plan parts in the series that validate transport/network behavior (see related parts for conformance test plans).

Typical use and users

Used by automotive OEMs, ECU and embedded-system engineers, Tier‑1 suppliers, diagnostic tool and test-house vendors, and laboratories implementing or testing CXPI-based networks. The standard is referenced when designing transport/network functionality for vehicle sensor/actuator networks where CXPI is chosen as the in-vehicle interface.

Related standards

ISO 20794 is a multipart series for the CXPI interface. Relevant parts include ISO 20794-2 (application layer), ISO 20794-4 (data link and physical layers), and multiple conformance test-plan parts (for application, transport/network, and data-link/physical conformance). Other numbered parts in the series (parts 5–7 and related documents) provide application and conformance test plans and complement the layer specifications in part 3.

Keywords

CXPI; Clock Extension Peripheral Interface; ISO 20794-3:2020; transport layer; network layer; automotive diagnostics; ECU; in-vehicle network; conformance testing; ISO/TC 22/SC 31.

FAQ

Q: What is this standard?

A: ISO 20794-3:2020 is the part of the ISO 20794 series that specifies the transport and network layers for the CXPI (Clock Extension Peripheral Interface) used in road vehicles.

Q: What does it cover?

A: It covers the services and protocols of the OSI transport and network layers for CXPI — how messages are formed into packets, control information and identifiers are added, error detection is performed, and how node addressing and timing are handled for diagnostic and node-configuration segments.

Q: Who typically uses it?

A: Automotive system architects, ECU designers, Tier‑1 suppliers, diagnostic-tool vendors, test laboratories and standards/quality engineers who implement or verify CXPI network behavior.

Q: Is it current or superseded?

A: The published 2020 edition (Edition 1) was reviewed and confirmed; the ISO record indicates this version remains current (confirmed in the periodic review).

Q: Is it part of a series?

A: Yes — ISO 20794 is a multipart standard for CXPI. Part 3 (this document) works together with parts covering the application layer, data-link and physical layers, and several conformance test-plan parts that validate implementations.

Q: What are the key keywords?

A: CXPI, transport layer, network layer, diagnostics, ECU, conformance test plan, ISO 20794, in-vehicle communication.