GMW GMW17655 PDF

Introduction

Note: Nothing in this standard supercedes applicable laws and regulations.

Note: In the event of conflict between the English and domestic language, the English language shall take precedence.

Purpose. The purpose of this standard is to clearly communicate the component requirements for the General Motors (GM) Heating Ventilation and Air Conditioning (HVAC) Local Interconnect Network (LIN) actuator.

Applicability. This standard is applicable to any HVAC actuator that utilizes an electrical architecture that requires LIN communication for proper HVAC actuator functionality.

Remarks.

This document describes the features of a bus system which permits communication between an Electronic Control Unit (ECU) and different actuators in a vehicle HVAC unit. The protocol is based on the bus protocol LIN 2.0.

The bus system refers to two types of devices, a Master and a Slave. A Slave is a device that is receiving or responding to a command. A Master is a device that issues commands, generates the synchronization, and manages the network. The system is then defined as a single Master and multiple Slaves.

The general features of this communication are as follows:

• Serial and unsynchronized transmission of bytes.

• Byte structure: 1 Start bit, 8 Data bits (Least Significant Bit (LSB) sent first), 1 Stop bit.

• Master transmission: (10 417 ± 0.5)%

• Slave transmission:

• Without synchronization (10 417 ± 15)%.

• With synchronization, ±2% of the Master timing.

• Each Node has diagnostic recognition and diagnostic processes.

• LIN bus max wire length up to 40 m.

Note: The capacity on the bus line in the complete system has to be adjusted to a value that results in the best possible immunity against radiated interference.