BMW E65 User Manual download pdf (Page 21)

E65 Bus Systems

Failsafe Characteristics

If the PT CAN goes into emergency mode it is no longer available for the engine control sys-

tem. However, it can still provide communication between the other bus nodes even if:

• One of the CAN leads (cores) is broken- one of the CAN leads (cores) is shorting to

ground.

• One of the CAN leads (cores) is shorting to the power supply B+.

"Wake-up" Lead in PT CAN Network

The PT CAN for the E65 is now a three wire CAN, the third wire is a hard wire KL-15 sig-

nal used to wake up the powertrain control units. The "wake-up" lead has nothing to do

with the actual PT CAN function. A wake-up telegram is still transmitted by the CAS via the

ZGM - PT-CAN as a CAN message.

Fiber-Optic Bus Lines

Introduction

Transmission of data, voice and images involves ever increasing volumes of data. Fiber-

optic technology (already in use in tele-communications and industrial installations) is capa-

ble of handling such large volumes of data while at the same time offering additional

advantages.

High data transmission rates in copper wires cause electromagnetic interference. This can

interfere with other vehicle systems. Compared with copper wires, fiber-optic lines require

less space and are lighter in weight for the same transmission band width. In contrast with

copper wires, which carry digital or analog voltage signals as the means of transmitting

data, fibre-optic busses transmit light. BMW uses plastic (POF-polymer optical fibers)

cables manufactured by Dow-Corning.

Advantages of Plastic Fiber-Optic Lines

Because of the large cross section of the fibers, the positioning of the fiber core does not

present a significant technical problem in production.

Relatively Low Sensitivity to Dust. Even with the most careful precautions, dust can find

its way onto the surface and alter the amount of light entering/leaving the optical fibre. Small

amounts of contamination do not result in communication failure.

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BMW E65 User Manual Page 21