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CAN Newsletter magazine

The first CAN networks in BMW cars

Two years after a point-to-point CAN network implementation, BMW introduced in 1995 a CAN network in star topology connecting five electronic control units (ECUs).

(Source: BMW)

The complete article is published in the March issue of the CAN Newsletter magazine 2020. This is just an excerpt.

BMW used already in 1993 in its 740i/iL model a 500-kbit/s CAN network linking the DME and EGS control units supplied by Bosch. The bus system substituted multiple serial links between these ECUs. This reduced cabling and avoided connection failures. Of course, it saved weight, too. In 1995, the German automaker equipped its E38 750iL model with a CAN network using a tree/star topology. It connected five ECUs: DME I, DME II, AGS, DCS, and EML. Three years later, the instrument cluster and the steering-angle sensor were added to the CAN network. The 1999 model of the 750iL was the last BMW car using shielded CAN cables. In the next models just twisted-pair cables were implemented. The wire color was uniform throughout the vehicle: CAN-L was GE/BR and CAN_H was GE/SW or GE/RT. The 120-Ω termination resistors were located in two ECUs between the CAN_H and CAN_L bus-lines. Usually, the resistors were equipped in the ASC/DSC unit and the instrument cluster of the DME unit.

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