ISO 11519-3:1994

Overview

ISO 11519-3:1994 - Road vehicles - Low-speed serial data communication - Part 3: Vehicle Area Network (VAN) - specifies the data link layer (LLC/MAC) and the physical layer for an automotive low-speed serial network (up to 125 kbit/s). The standard defines a multimaster–multislave, access-method oriented network that optimizes request/response exchanges by permitting a remote transmission request with in-frame response insertion (retaining medium access to allow the responder to insert data).

Key topics and technical requirements

• Scope: Defines general VAN architecture and the complete content of Layer 2 (data link) and Layer 1 (physical) for on-board vehicle electronic modules.
• Data rates: Targeted for low-speed communications up to 125 kbit/s.
• Layer mapping: Conforms to the OSI model with clear breakdown into LLC (Logical Link Control) and MAC (Medium Access Control) sublayers, plus the physical signalling/encoding and line interface.
• LLC services:
  • Unacknowledged data transfer (efficient point-to-point, multipoint, broadcast)
  • Acknowledged data transfer (reliable point-to-point; LLC Type 3 functions referenced but not fully specified)
  • Remote data transmission (request/response mechanisms including in‑frame responses)
• MAC features:
  • Frame structure (SOF, identifier, command, data, FCS/CRC, ACK, EOF, IFS)
  • Medium access method including bitwise arbitration using dominant/recessive bus states so higher-priority messages win collisions
  • In-frame acknowledgement and chaining responses
• Physical layer:
  • Bit/symbol encoding, synchronization, line transmitters/receivers, connectors and communication medium
  • Electrical parameters and conformance tests for transmitter/receiver behaviour
• Conformance & testing: Procedures for MAC and physical layer conformance; annexes provide setup examples and interface details.

Practical applications and who uses it

ISO 11519-3 is intended for:

• Automotive systems engineers and architects designing low-speed in‑vehicle networks for body electronics, diagnostics, sensors and actuator modules
• OEMs and Tier‑1 suppliers implementing interoperable electronic control units (ECUs)
• Firmware and hardware developers implementing LLC/MAC and physical interfaces (encoders/decoders, transceivers)
• Test labs and quality engineers validating conformance to MAC and physical layer requirements

Practical benefits include improved interoperability between heterogeneous modules (including very simple slave devices), prioritized messaging through arbitration, optimized request/response exchanges, and defined conformance tests for reliable vehicle integration.

Related standards

• ISO 11519 (general series on low-speed serial data communication)
• ISO 11519‑2 (Low‑Speed Controller Area Network - CAN)
• ISO 8802‑2 (LLC reference for LAN architecture)

Keywords: ISO 11519-3, Vehicle Area Network, VAN, low-speed serial data, automotive networking, data link layer, physical layer, MAC, LLC, remote transmission request, in-frame response, 125 kbit/s.