ISO 11992-1:2019

Overview

ISO 11992-1:2019 - "Road vehicles - Interchange of digital information on electrical connections between towing and towed vehicles - Part 1: Physical and data-link layers" defines the lower OSI-layer requirements for CAN-based communication between towing and towed vehicles (typically vehicles with maximum authorised total mass > 3 500 kg). This third edition updates the data link layer (DLL) and physical layer (PHY) definitions for safe, interoperable digital interchange over the electrical connection (cabling and connectors) between tractor and trailer.

Key points:

• Covers the Data Link Layer (DLL) and Physical Layer (PHY) split into Physical Signalling (PS), Physical Medium Attachment (PMA) and Physical Medium Dependent (PMD) sub-layers.
• Targets CAN-based interfaces used across the ISO 11992 series.
• Adds clarifications, requirement statements and an informative Annex A on bus failure management.

Key Topics and Requirements

• Data Link Layer (DLL)
  • Compliance with ISO 11898-1 is required for the DLL protocol entity (REQ 2.1).
  • Frame format restriction: devices shall transmit only data frames in CEFF (Classical Extended Frame Format) (REQ 2.2).
  • No remote-frame requests: DLL device interfaces shall not request data via remote frames (REQ 2.3).
• Physical Layer (PHY)
  • Divided into PS, PMA and PMD sub-layers.
  • PS (Physical Signalling): PS entity and device interfaces shall conform to ISO 11898-1; bit-timing settings determine transmission speed and resynchronisation capability. Fault confinement behavior follows ISO 11898-1 (REQ 1.1, REQ 1.2).
  • PMA (Physical Medium Attachment): typically implemented in the CAN transceiver or System Base Chip (SBC); may include protective circuitry.
  • PMD (Physical Medium Dependent): connectors, cabling and electro-mechanical components that implement the media-dependent sub-layer.
• Network and device interface requirements and numbered requirement statements for traceability and implementation.

Applications and Who Uses It

ISO 11992-1:2019 is intended for:

• OEM engineers and vehicle network architects designing towing–towed communications (tractor–trailer).
• CAN controller and CAN transceiver (PMA) developers.
• Electronic Control Unit (ECU) and System Base Chip (SBC) designers.
• Wiring harness, connector and cabling manufacturers (PMD scope).
• Vehicle integrators, fleets and maintenance/diagnostics teams implementing compliant diagnostic and communication frameworks.

Practical uses include secure transfer of braking, lighting, diagnostics and other vehicle control data across the electrical coupling between towing and towed units.

Related Standards

• ISO 11898-1 (CAN data link layer and physical signalling) - normative reference
• Other ISO 11992 parts (application-layer, diagnostics): ISO 11992-2, -3, -4
• Vehicle diagnostics and transport layers: ISO 14229 series, ISO 15765-2, ISO 7638-1, ISO 12098

Keywords: ISO 11992-1:2019, CAN, data link layer, physical layer, towing and towed vehicles, CAN transceiver, PMA, PMD, PS, vehicle networks, electrical connections, tractor–trailer communication.