SAE J1939 is a communication standard for electronic control units (ECUs) in commercial vehicles, ensuring interoperability across manufacturers. The J1939 software stack, developed by Embitel Technologies, features a layered architecture compliant with the standard, supporting network management, diagnostics, and reprogramming services. It includes specifications for message formats, parameter groups, and diagnostic trouble codes to facilitate vehicle diagnostics and communication.

1. Embitel Technologies International presence:
What is J1939 Software Stack?

2. Embitel Technologies International presence:
 SAE J1939 is a software standard defined by Society of Automotive
Engineers (SAE). This software standard has been designed to
ensure that Electronic Control Units (ECU) manufactured by
different automotive suppliers are able to communicate with each
other within an in-vehicle network.
 SAE J1939 standard is defined for applications in commercial
vehicles for CAN (Controller Area Network) bus.
What is SAE J1939 – an introduction?

3. Embitel Technologies International presence:
 J1939 stack is an embedded software stack with layered architecture, compliant with
SAE J1939 standard.
 This pre-tested software stack, designed by our embedded automotive engineers, can
be easily integrated with commercial vehicle applications for diagnostics and
communication services.
 Our product engineering team has also developed J1939 bootloader for automotive
ECU reprogramming services.

4. Embitel Technologies International presence:
J1939 layered architecture specifications – as defined by SAE
.

5. Embitel Technologies International presence:
 J1939/21 – Data Link/ Transport Layer: This layer defines the Message/Frame Format, Protocol Data
Unit (PDU) Formats, Message Type, Message Priority, Bus Access, Arbitration, Error Detection, PGNs
and Transport Protocol Functions
 J1939/81 – Network Management Layer: This layer defines Name ECU, Address, Network
Management Procedure, Network Error Management, Address Claim and ECU Initialization
procedures
 J1939/71 – Vehicle Application Layer: This layer defines Parameter Group Numbers (PGNs), Suspect
Parameter Numbers (SPNs) with the Scaling, Limits and Parameter Offset Size.
 J1939/73 — Application Layer for Diagnostics services: This layer defines Diagnostic Trouble Codes
(DTC), Diagnostic Parameter Group Definitions and Diagnostic Messages (DM)
(Source: SAE)
Following are the details:

6. Embitel Technologies International presence:
 Enables in-vehicle network communications (ECU communications)
 Supports vehicle diagnostics services and fault-code memory.
 J1939 bootloader supports in-vehicle ECU reprogramming.
 The embedded software code of the Stack is MISRA-C complaint.
Features of the reusable J1939 stack:

7. Embitel Technologies International presence:
When certain failure occurs in an automotive ECU, it is noted in the form of a
Diagnostic Trouble Code (DTC), also known as Fault Code. DTCs’ are defined by
SAE J1939 standard.
Diagnostic Trouble Code (DTC) has the following fields:
What is Diagnostic Trouble Code (DTC) in J1939 stack

8. Embitel Technologies International presence:
SPN is Suspect Parameter Number (19 bits)
FMI is Failure Mode Identifier (5 bits)
OC is Occurrence Count (7 bits)
CM is SPN Conversion Method (1 bit).
Few examples are listed below
SPN = 91 Suspect parameter is accelerator pedal position
FMI = 3 Failure mode is identified as voltage above normal
OC = 9 Occurrence count indicates trouble has occurred 9 times
CM = 0 Conversion Method is Intel.
With help of DTC one can understand failure that has been reported.

9. Embitel Technologies International presence:
• J1939 is a standard (set of embedded software specifications) defined by SAE
(Society of Automotive Engineers). The SAE J1939 protocol specifications are
defined for CAN bus, and J1939 stack is an embedded software code with
layered architecture and is compliant with J1939 standard.
• To know more about our J1939 stack solutions and services mail
to sales@embitel.com