SAE J1708 Test Protocol for Data Link Diagnosis

Automotive Tests

SAE J1708 Test Protocol for Data Link Diagnosis


The J1708 Protocol is an SAE specification developed specifically for heavy-duty vehicles (trucks and buses). The goal is for the protocol to develop a standard for serial communication between modules with microcontrollers. The standard means that data can be transferred between devices more cost-effectively. Other advantages:

SAE J1708 Test Protocol for Data Link Diagnosis

Minimizes hardware cost.
It offers flexibility and the possibility of further expansion of an existing system.
It uses standard industry electronics giving more options during development.

SAE J1708 Usage Areas

Because the J1708 protocol defines only the lower layers of the OSI model, it is always used with an overlapping application layer. An example of such a layer is J1587, which is used in heavy-duty vehicles to exchange data between microcontrollers.

The protocol describes both physical properties such as how the voltage level on the bus should be interpreted and how messages are generated.

  • It defines the physical and data link layer according to the OSI model.
  • It is almost always used in conjunction with the application layer protocol SAE J1587.
  • It is based on the electronics from the RS-485 bus.
  • Twisted pair wire with a maximum length of 40 m.
  • The network is based on a bus topology.
  • Serial byte oriented communication with least significant byte first.
  • The transmission rate is 9600 bps.

A message includes:

One byte long MID (Message Identification), followed by a series of data bytes, and finally a checksum. A message can be up to 21 bytes long. Error detection and handling in collision of message transmission.

EUROLAB laboratory, with its professional engineer staff, provides the best service to our suppliers and manufacturers with 1708 years of experience within the scope of SAE J25 data line diagnosis test protocol.

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