ISO 20794-3:2020 PDF

Road vehicles — Clock extension peripheral interface (CXPI) — Part 3: Transport and network layer

Open preview (PDF)

Title (English):

ISO 20794-3:2020

Road vehicles — Clock extension peripheral interface (CXPI) — Part 3: Transport and network layer

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 23
Publication date:: February 5, 2020
Edition:: ISO IS 20794 edition 1 version 1
ICS:: 43.040.15

Delivery type:

Full version25 €Read online 24h10 €Read online 72h15 €

Document language:

enru

Delivery time:Immediate download

Price:25 €

Description (English):

This document specifies the OSI transport layer and network layer by means of services and protocols. They can be used by different applications. The transport layer: — transforms a message into a single packet; — adds protocol control information for diagnostic and node configuration into each packet; — adds packet identifier for diagnostic and node configuration into each packet; and — performs transport protocol error detection. The transport layer protocol is not used for normal communication except to map the service interface parameters between lower and upper OSI layers. The network layer: — adds a node address for diagnostic and node configuration into each segment; and — observes timing for diagnostic and node configuration of each segment. The network layer is not used for normal communication except to map the service interface parameters between lower and upper OSI layers.

Technical details

Technical committee: ISO/TC 22/SC 31 - Data communication
SKU: ISO 20794-3:2020

Abstract

Overview

ISO 20794-3:2020 defines the transport layer and network layer for the CXPI (Clock Extension Peripheral Interface) in-vehicle network. CXPI is a low-speed, single‑wire automotive bus (up to 20 kbit/s) intended for simple devices such as switches and sensors to reduce wiring, weight and cost. This part of ISO 20794 specifies services, protocols and interfaces that transform application messages into CXPI packets and segments for diagnostic and node-configuration use, and it maps service interface parameters between adjacent OSI layers.

Key technical topics and requirements

Transport layer (TL)
- Transforms an application message into a single packet (T_PDU).
- Adds protocol control information and a packet identifier for diagnostic and node configuration.
- Performs transport-layer error detection.
- Not used for normal vehicle communication except to map service interface parameters between lower and upper OSI layers.
- Service interfaces include T_Data.req / T_Data.ind and parameter mappings for packet types (NormalCom, DiagNodeCfg).
Network layer (NL)
- Adds a node address (N_NAD) into each segment (N_PDU) for diagnostic and configuration traffic.
- Observes and enforces timing constraints for diagnostic and node-configuration exchanges.
- Also primarily a mapping layer between lower and upper OSI layers for non-normal communication.
- Service interfaces include N_Data.req / N_Data.ind with parameter mappings.
Service Interface Parameters (SIP) - standardized parameters used across TL/NL:
- Examples: TA (target address), SA (source address), Ptype (packet type), ReqId, ReqTypeId, PDU, Length, NMInfo, SCT (sequence count), Result.
Functional models and timing
- Transmission and reception logic, timing parameters and constraints, and error detection mechanisms are defined to ensure interoperability and robust diagnostic messaging.

Practical applications and who uses the standard

Typical applications: door control modules, lighting switches, HVAC controls, and other low-bandwidth sensor/actuator nodes.
Primary users: automotive OEMs, tier‑1/2 suppliers, ECU/network architects, firmware developers, diagnostic tool vendors, test & validation engineers, and compliance/certification teams.
Practical value: ensures consistent transport/network behavior for diagnostic and node‑configuration messages across CXPI devices, enabling reliable diagnostics, node addressing, timing coordination and interoperability.

Related standards

Other parts of ISO 20794 (physical, data link, application, conformance testing) and diagnostic standards such as ISO 14229 (UDS) are referenced for full CXPI system implementation and vehicle diagnostic frameworks.

Keywords: ISO 20794-3, CXPI, transport layer, network layer, in-vehicle network, single-wire, diagnostic, node configuration, OSI.

Related standards

Mentioned in the description and other ISO standards

Abstract

Overview

Key technical topics and requirements

Transport layer (TL)
- Transforms an application message into a single packet (T_PDU).
- Adds protocol control information and a packet identifier for diagnostic and node configuration.
- Performs transport-layer error detection.
- Not used for normal vehicle communication except to map service interface parameters between lower and upper OSI layers.
- Service interfaces include T_Data.req / T_Data.ind and parameter mappings for packet types (NormalCom, DiagNodeCfg).
Network layer (NL)
- Adds a node address (N_NAD) into each segment (N_PDU) for diagnostic and configuration traffic.
- Observes and enforces timing constraints for diagnostic and node-configuration exchanges.
- Also primarily a mapping layer between lower and upper OSI layers for non-normal communication.
- Service interfaces include N_Data.req / N_Data.ind with parameter mappings.
Service Interface Parameters (SIP) - standardized parameters used across TL/NL:
- Examples: TA (target address), SA (source address), Ptype (packet type), ReqId, ReqTypeId, PDU, Length, NMInfo, SCT (sequence count), Result.
Functional models and timing
- Transmission and reception logic, timing parameters and constraints, and error detection mechanisms are defined to ensure interoperability and robust diagnostic messaging.

Practical applications and who uses the standard

Typical applications: door control modules, lighting switches, HVAC controls, and other low-bandwidth sensor/actuator nodes.
Primary users: automotive OEMs, tier‑1/2 suppliers, ECU/network architects, firmware developers, diagnostic tool vendors, test & validation engineers, and compliance/certification teams.
Practical value: ensures consistent transport/network behavior for diagnostic and node‑configuration messages across CXPI devices, enabling reliable diagnostics, node addressing, timing coordination and interoperability.

Related standards

Other parts of ISO 20794 (physical, data link, application, conformance testing) and diagnostic standards such as ISO 14229 (UDS) are referenced for full CXPI system implementation and vehicle diagnostic frameworks.

Keywords: ISO 20794-3, CXPI, transport layer, network layer, in-vehicle network, single-wire, diagnostic, node configuration, OSI.

ISO 20794-3:2020 PDF

Technical details

Abstract

Overview

Key technical topics and requirements

Practical applications and who uses the standard

Related standards

Related standards

Abstract

Overview

Key technical topics and requirements

Practical applications and who uses the standard

Related standards

Related standards

Road vehicles — Clock extension peripheral interface (CXPI) — Part 4: Data link layer and physical layer

Road vehicles — Unified diagnostic services (UDS) — Part 3: Unified diagnostic services on CAN implementation…

Systems and software engineering — Software life cycle processes

Asset management — Vocabulary, overview and principles

Asset management — Asset management system — Requirements

Information technology — Radio frequency identification device conformance test methods — Part 2: Test method…

Information technology — Multimedia framework (MPEG-21) — Part 22: User Description

Milk — Determination of the lactoperoxidase activity — Photometric method (Reference method)