1997 MERCEDES-BENZ ML320 Complete Repair Manual

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Page 1505 of 4133

MERCEDES-BENZ ML320 1997 Complete Repair Manual 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 utilize

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
me
Saturday, October 02, 2010 3:30:04 PMPage 10 © 2006 Mitchell Repair Information Company, LLC.

Page 1506 of 4133

MERCEDES-BENZ ML320 1997 Complete Repair Manual 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) h

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
Saturday, October 02, 2010 3:30:04 PMPage 11 © 2006 Mitchell Repair Information Company, LLC.

Page 1507 of 4133

MERCEDES-BENZ ML320 1997 Complete Repair Manual DATA TRANSFER, FUNCTION - GF82.00-P-2000A
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
The Digital Data Bus (D2B) contains the master u

DATA TRANSFER, FUNCTION - GF82.00-P-2000A
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
The Digital Data Bus (D2B) contains the master unit, e.g. the radio (A2) except for model 129, and model 202,
which triggers all the components in the Digital Data Bus system (D2B). The master unit also serves as an
interface (Gateway) to the CAN interior (CAN-B). For this purpose, signals arriving at the master unit are
converted so that they can be transmitted from the Digital Data Bus (D2B) to the CAN interior (CAN B) and
vice versa. Moreover, the master unit serves as a timing circuit which provides the clock pulse with which the
information frames are transferred on the Digital Data Bus (D2B). A frame consists of 2 subframes. A series of
many data frames contains the complete information for proper operation of the components located at the
Digital Data Bus (D2B). The conversion of optical pulses into electrical signals and vice versa is done by
transmitter and receiver diodes, that are integrated into each component. Each of the components receives or
transmits the electrical signals from the chip of the Digital Data Bus system (D2B) as a "D2B log". Source data
and control data are transmitted.
The source data are transferred synchronously, for example as present on a music CD, as 32 bit blocks into the
subframes. By contrast, control data are transferred asynchronously. They are divided up (2 bits per subframe)
and distributed over several subframes. The control data are provided with an address, which indicates for
which components the data are intended in the Digital Data Bus (D2B). The individual data packages are joined
together again in the components and they can then be processed. A data frame can therefore contain highly
differing types of information (source and control data from all components mounted in the digital data bus
(D2B)). The transmission and reception diodes as well as the digital data bus (D2B) chip are switched off when
not required in order to reduce the quiescent current (sleep mode). Switch-off is accomplished immediately
when the master unit or circuit 15 is switched off. After restart, the digital data bus system (D2B) can be
activated either by the components or by the master unit by means of an electrical signal in the wake-up line for
optical data transmission.
Regardless whether the information is intended for a component, it feeds an edited light signal back into the
digital data bus (D2B) at full intensity (repeater function).
WAKE-UP, FUNCTION - GF82.00-P-2001A
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
Normal wake-up
Digital data bus (D2B), function GF82.00-P-0001A
Data transfer, function GF82.00-P-2000A
Wake-up, function GF82.00-P-2001A
Survey of system components, digital
data bus (D2B),
location/task/design/function GF82.00-P-9999A
Wake-up, function GF82.00-P-2001A

2001 Mercedes-Benz ML320
1998-2005 ACCESSORIES & BODY, CAB Electrical System - Body - 163 Chassis
me
Saturday, October 02, 2010 3:30:04 PMPage 12 © 2006 Mitchell Repair Information Company, LLC.

Page 1508 of 4133

MERCEDES-BENZ ML320 1997 Complete Repair Manual Since the transmitting and receiving diodes along with the digital data bus systems (D2B) chip are
automatically shut off if they are not needed (sleep mode), a wake-up pulse, which activates the sy

Page 1509 of 4133

MERCEDES-BENZ ML320 1997 Complete Repair Manual Fig. 6: Identifying Fiber Optic Cable Components Location
FIBER OPTIC CABLE, FUNCTION - GF82.00-P-4000-04A
The fiber optical cable consists of plastic with a fiber diameter of 1 mm. Each fiber optic

Page 1510 of 4133

MERCEDES-BENZ ML320 1997 Complete Repair Manual Exemplified on model 215 with code (819) 6-disc CD changer, with code (810) Sound System and with
code (382) MB phone "CTEL" in console on right side of dome
Fig. 7: Identifying Fiber Optic Cable,

Page 1511 of 4133

MERCEDES-BENZ ML320 1997 Complete Repair Manual HEADLAMP RANGE ADJUSTMENT (HRA), LOCATION OF COMPONENTS - GF82.10-P-0001-01GH
Fig. 8: Identifying Headlamp Range Adjustment (HRA) Components
HEADLAMP RANGE ADJUSTMENT (HRA), LOCATION OF COMPONENTS -

Page 1512 of 4133

MERCEDES-BENZ ML320 1997 Complete Repair Manual Fig. 9: Identifying Headlamp Range Adjustment (HRA) Components
HEADLAMP RANGE ADJUSTMENT (HRA), FUNCTION - GF82.10-P-0001GH
MODELS 163.113 /136 /154 /172 /174 up to 31.8.01 with CODE (612b) Xenon he

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