Mercedes-Benz ML320. Manual — part 218

Fig. 3: Identifying Position Of Identification On Fiber Optic Cable Wiring Harness

Routing

The inserts (5) of the fiber optic cable modules may only be routed as in production. The fiber optic cable
modules must always be provided with a protective cap when routing. For every vehicle model, the sequence of
components in the D2B ring is specifically predetermined. The components are connected by fiber optic cable
modules. They are secured to a wiring harness with an orange-colored casing.

Fig. 4: Identifying Fiber Optic Cable Modules Insert

Danger of breaking! Do not kink fiber optic cable, route over sharp edges or bend in radii smaller than 25

mm. Tensile forces on inserts must not exceed 65 N.

The fiber optic cable must not be exposed to temperatures greater than 85°C or lower than -40°C. Do not
squeeze fiber optic cable, in other words do not compress with clamps or cable ties.

Connection between the devices

The Digital Data Bus ring (D2B) connects the new radio generation and COMAND (monitor) to the CD
changer (CDC) (USA preinstallation), telephone and portable CTEL. The sound amplifier remains wired as
COMAND (monitor) to the CD changer (CDC) (USA preinstallation), telephone and portable CTEL. The sound
amplifier remains wired as before with Models 129, 170, 202, 208 and 210. The radio and COMAND as head
unit (HU) performs the master function and also forms the interface to the Control Area Network bus Class B
(interior) (CAN-B) (for vehicles with multifunction steering wheel).

Ring sequence of vehicles/models/interface

2001 Mercedes-Benz ML320

1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis

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Model 129 HU - telephone (or Tele Aid) - CDC - HU

Model 163 HU - Sound - CDC - telephone (or TELE AID) - HU

Model 168 HU - telephone - CDC - HU

Model 170 HU - telephone - HU (ECE); HU - CDC - HU (Japan)

Model 202/208 HU - CDC - telephone (or Tele Aid) - VCS - HU

Model 203/209 HU - sound - portable CTEL interface - VCS - CDC - HU

Model 210 HU - CDC - VCS - telephone (or TELE AID) - HU

Model 215/220 HU - sound - CDC - telephone (or Tele Aid) - VCS - optional portable CTEL interface - HU

Model 230 HU - Sound - CDC - Telephone (or TELE AID) - SBS - HU

Model 414/463 HU - CDC - telephone - HU

The sequence represents the current maximum equipment. If special equipment (SA) is omitted, the

respective item is deleted, resulting in a new ring sequence.

Read out actual configuration using STAR DIAGNOSIS

As of September 1999 it is possible to read out the current actual configuration of a functioning D2B ring by
means of STAR DIAGNOSIS. This is particularly important in the case of later expansion of the D2B ring and
when retrofitting D2B components e.g. telephone.

In the diagnosis system there is the menu item "Retrofitting D2B components". Under this menu item, the
current actual configuration of a vehicle can be read out and written back immediately as a new nominal
configuration. The process is self-explanatory.

BASIC KNOWLEDGE

DIGITAL DATA BUS (D2B), FUNCTION - GF82.00-P-0001A

MODEL 129 as of 1.6.98, 163, 168 as of 1.9.98, 170, 202 as of 1.6.98, 203, 208, 210 as of 1.6.98, 215, 220

Component sequence, exemplified on model 220 with code (819) 6-disc CD changer, with code (810)
sound system, with code (813) voice control system (VCS) and with code (855) TELE AID

2001 Mercedes-Benz ML320

1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis

me

Fig. 5: Identifying Digital Data Bus (D2B), Function

Digital Data Bus (D2B)

The Digital Data Bus (D2B) is a data transmission system for the communication and information components,
which utilizes the optical data transfer options. Data transfer is conducted by means of optical pulses, which are
transferred over fiber optical cables to the connected communication and information components. Audio and
command signals are converted in the source components into optical pulses and transmitted via fiber optical
cables. The optical signal is converted back to an electronic signal in the target component. Because of the high
transfer rate, the Digital Data Bus (D2B) can transfer audio and command signals simultaneously. Simultaneous
transfer of source data and command data over the Digital Data Bus (D2B) significantly reduces the amount of
cabling. The connected components require 2 lines for the voltage supply (electrical) and 2 lines (input/output)
for the fiber optical cable of the Digital Data Bus (D2B) and one line for the wake-up signal (electrical).

In addition to this the fiber optical cable can transfer several pieces of source data simultaneously (e.g. music
and voice from 2 components), without compromising the data content.

Functional sequence on example of "Play CD" on model 220

Pressing "Play" on the radio (A2) sends a command signal over the Digital Data Bus (D2B) to the CD player
with changer (in trunk) (A2/6), for vehicles with code (819) 6-disc CD changer. The audio signals from the CD
player with changer (in the trunk) (A2/6), for vehicles with code (819) 6-disc CD changer, are then sent over the
Digital Data Bus(D2B) as source data to the Sound amplifier (A2/13), or for vehicles with code (810) to the
sound system. The target components, the Sound amplifier (A2/13), or for vehicles with code (810) the sound
system, the source data are then converted back to electrical signals and reproduced as sound.

Data transfer using fiber optic cables has the following advantages:



Extremely high data transmission rate



Prevents tapping and cross talk



Insensitive to electromagnetic radiation

2001 Mercedes-Benz ML320

1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis

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

Short-circuit resistance



Zero potential connection of components



No oxidation



Low weight of fiber optical cable



Minimum diameter of wiring harness

The digital data bus (D2B) has a closed ring structure. The communication and data components are arranged
here in a distributor line (in-series circuit). This arrangement is type specific and is illustrated by way of an
example on model 220 as follows:



Radio (A2)



CD player with changer (in trunk) (A2/6), with code (819) 6-disc CD changer



Sound amplifier (A2/13), with code (810) Sound System



Voice control system control unit (A35/11), with code (813) voice control system (VCS)



Telephone and TELE AID transmitter/receiver, D2B (A35/17), with code (855) TELE AID

Data transfer is conducted here in one direction only, i.e. the optical pulses for the voice control system control
unit (A35/11), for vehicles with code (813) voice control system (VCS), on model 220 pass through all
components connected to the ring, before arriving at the target components.

When the system is first put into operation, a system test is performed. In doing so the individual components
and their sequence in the ring structure of the Digital Data Bus (D2B) are registered by the component with the
master function.

A type-specific sequence is stored ex-factory. In turn, the storing of a sequence ex-factory means: if the radio
(A2) is taken from one model series and installed into another one, then during a system test the different
sequence of the components and an error message are filed in the diagnostic trouble code memory.

An error message is also filed if the radio (A2) is exchanged within a model series with different equipment
components. The system goes to the operational state regardless of the error message. STAR DIAGNOSIS
enables the sequence of the components to be subsequently altered in the Digital Data Bus (D2B).

The Digital Data Bus (D2B) is diagnosis capable via the data link connector (X11/4), except for models 129

and 202.

The operating principle of the Digital Data Bus (D2B) is the same for all model series; all that changes is the

sequence of components depending on the national version and equipment specification.

TABLE OF CONTENTS, FUNCTION DESCRIPTION OF DIGITAL DATA BUS (D2B) - GF82.00-P-0999ZZ

MODEL 129 as of 1.6.98, 163, 168 as of 1.9.98, 170, 202 as of 1.6.98, 203, 208, 210 as of 1.6.98, 215, 220

Data transfer, function

GF82.00-P-2000A

2001 Mercedes-Benz ML320

1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis

me