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SAE Technical Paper Series [SAE International International Congress & Exposition - (MAR. 01, 1999)] SAE Technical Paper Series - Gateway Application for Automotive Network System “BEAN”

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جلد:
1
سال:
1999
زبان:
english
DOI:
10.4271/1999-01-1278
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SAE TECHNICAL
PAPER SERIES

1999-01-1278

Gateway Application for Automotive Network
System "BEAN"
Akihiro Tanaka, Masachika Kamiya and Kazunori Sakai
TOYOTA MOTOR CORPORATION

Tomohisa Kishigami
DENSO CORPORATION

International Congress and Exposition
Detroit, Michigan
March 1-4, 1999
400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A.

Tel: (724) 776-4841 Fax: (724) 776-5760

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1999-01-1278

Gateway Application for Automotive Network System "BEAN"
Akihiro Tanaka, Masachika Kamiya and Kazunori Sakai
TOYOTA MOTOR CORPORATION

Tomohisa Kishigami
DENSO CORPORATION
Copyright © 1999 Society of Automotive Engineers, Inc.

ABSTRACT

bilateral communication in 1994. BEAN has been developed and launched in 1997. BEAN is communication protocol that is low cost, low quiescent drain to drive and
secure response characteristics for less frequent data
transmission.

In applying a LAN to automotive electronics systems, an
optimal protocol has been adopted for each system so
far, such as body electronics system, entertainment system, service system and power train system. As low cost
communication protocol ”BEAN” (Body Electronics Area
Network; SAE paper 970297) adopted to wider range of
functions on vehicle, ECU’s numbers are increased
which have BEAN communication and that is branched to
plural communication networks. We have succeeded in
rationalization of those network systems with the gateway
function on a delegated ECU for each LAN system on
vehicle. And this system also realized the connection to
after market products by data exchange through the
gateway function, while securing vehicle fail-safe.

By the expansion of BEAN application to automotive
electronics systems, ECU’s numbers are increased which
are connect to BEAN communication lines that is
branched to plural communication networks. It is also
required for after market products to connect to that communication network.

RATIONALITY OF VEHICLE LAN MOUNTED
GATEWAY FUNCTION
GATEWAY BETWEEN ENTERTAINMENT LAN AND
BODY CONTROL SYSTEM LAN – It’s difficult to combine entertainment LAN had registration function for adding dealer-installed options to body control system LAN
was required hi-response and had different operating
power supply. The following to the vehicle control functions are connected with these two LANs.

INTRODUCTION
In applying a LAN to automotive electronics systems,
these have been developed independently in several
technical fields. We have introduced total control network, which is J1850 type of protocol since 1991. Since
then, we are now developing the standard communication protocol that is suitable for high speed and periodically timing communication. That aims to simplify the
optional connection and harmonized control in between
power train system and chassis control system and so
on. For entertainment system, its communication technology has been developed in order to be common connection method with the combination by components
such as audio and navigation, communication and also
after market product connection since 1994. For service
system, its development has originally started with the
legal requirement on diagnostics. Then it has been
improved since 1994 in order to become common connection to tester tools and enhance diagnostic contents.

• Operation of air-conditioner on multi-display
• Interactive control of navigation system and engine
• Integration of body control switches and audio control
switches
To mount the gateway function on representative ECU
that communicated between each LANs enables to
reduce communication circuit parts and to decrease
communication software load.

For body control system, single way communication to
the driver’s door ECU from body ECU has been adopted
since 1992 in order to reduce wire harness to the door
and function enhancement by information sharing
between ECUs. After that plural ECUs have adopted

Figure 1. An Example of Construction between
Entertainment LAN and Body Control System
LAN
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LAN. The following points should be taken into consideration in selecting such an ECU:

GATEWAY BETWEEN SERVICE LAN AND BODY
CONTROL SYSTEM LAN – To enhance serviceability, it
is essential to improve the diagnostic function. Conventionally, there are many cases in which a diagnostic tool
cannot be used for diagnosing body control ECUs,
because of a relatively small system size and cost restrictions. The matter is as good as after introduction of invehicle LAN. Since it’s difficult to combine body control
system LAN was required hi-response to service LAN
was required standard, it’s necessary for connecting a
diagnostic tool to mount communication circuit and wiring. In this case, diagnostic tool is connected with many
LANs. By mounting gateway function on representative
ECU can be connected diagnostic tool enables communication of diagnostic frame format between the body control system LAN and diagnostic tool, resulting in the
following advantages:

• Allowance for gateway processing software load
• Reduced traffic in each communication line
In the above-mentioned application example, data is concentrated in the display. We have therefore decided to
mount the gateway function in the display. An example
construction is shown below.

• Only one ECU has to be connected to the diagnostic
tool. It is not necessary, therefore, to install additional hardware for diagnosis result outputs for multiple ECUs.
• Service LAN communication software is not required
for each LAN.
Figure 3. An Example of Construction between BEAN
and Entertainment LAN
Protocol conversion – An example frame conversion is
presented below.
The entertainment LAN uses IE-BUS protocol. Since the
IE-BUS can handle longer data blocks than BEAN, the
BEAN frame format is inserted in the data block of the IEBUS frame format as shown in Figure 4, to enable the
gateway ECU to process all data regardless of content.

Figure 2. An Example of Construction between Service
LAN and Body Control System LAN
GATEWAY BETWEEN BODY CONTROL SYSTEM LAN
AND DEALER-INSTALLED OPTION LAN – Connection
of dealer-installed options is indispensable to satisfy the
diversifying needs of automobile users. For wiring to
each optional ECU, it is necessary to connect joints to
the cables of existing switches and actuators. If an invehicle LAN is introduced, it is possible to obtain various
signals through the LAN.
In connection of dealerinstalled options, adverse influence of defective wiring of
the vehicle is considered. It can be avoided by connecting gateway function ECU isolated each bus electrically.

DESIGN OF GATEWAY FUNCTIONS
Each of the above-mentioned three gateway functions
have been designed as follows.
SPECIFICATION
ENTERTAINMENT
SYSTEM LAN

OF
LAN

GATEWAY
AND BODY

Figure 4. An Example of Frame Conversion

BETWEEN
CONTROL

This type of gateway function has been achieved simply:
both LANs access data using the CSMA/CD system,
both provide close communication speeds, and both are
required to handle a relatively small amount of gateway
data.

Position of the gateway function – The gateway function
should be implemented in an ECU that requires data
from both entertainment LAN and body control system

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only performs simple frame conversion as a relay, and
does not process data according to the content, which is
important in view of ensuring future expandability.

SPECIFICATION OF GATEWAY BETWEEN SERVICE
LAN AND BODY CONTROL SYSTEM LAN – This section describes the method of transmitting data from a
diagnostic tool to a gateway ECU connected to the body
control system LAN.

ISO 9141 protocol uses a master and slave, with a tool as
the master, whereas BEAN uses the CSMA/CD system.
These two protocols differ in basic characteristics. The
ISO 9141 specifies the timing at which a slave (target
ECU) responds to a request from the master (tool). For
BEAN, on the other hand, it is difficult to specify an exact
communication delay time, since it uses the CSMA/CD
system to access data. To the request that an ISO 9141based master transmits to a slave, the slave is required to
respond within 50 ms. With the construction shown in
Figure 5, however, there is a possibility that the slave
cannot respond within the specified time, due to the time
required for data transmission from the body control ECU
to the target ECU, and from the target ECU to the body
control ECU.

Method of connecting diagnostic tool – Figure 5 shows
an example construction in which a diagnostic tool is connected via the body control ECU.

Figure 5. An Example of Construction between BEAN
and ISO 9141
Basic operations are as follows:
1. Request frame for a target ECU is transmitted from
the diagnostic tool to the body control ECU.
2. The body control ECU converts ISO 9141 frame format to BEAN frame format.
3. The target ECU transmits data in response to the
request from the diagnostic tool.
Figure 7. Message Latency

4. The body control ECU converts BEAN frame format
to ISO 9141 frame format.
5. The diagnostic tool receives the response sent by the
target ECU via the body control ECU.
An example conversion between ISO 9141 and BEAN
frame formats is shown below.

Figure 8. Operation Latency

Figure 6. An Example of Frame Conversion

Use of negative response – The service tool has the
function of receiving negative response.
Negative
response provides the specification for extending the
time-out value in cases where a response cannot be
transmitted within the specified time.

ISO 9141 frame format comprises 11 bytes: 3bytes of
header and a maximum of 8 bytes of data. Since the
BEAN data length is variable to a maximum of 11 bytes,
the entire ISO 9141 frame format can be included as data
in the BEAN frame format. Except at initialization, the
ECU serving as a gateway between ISO 9141 and BEAN

An example of an operation sequence involving a negative response is shown below with reference to Figure 9.
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1. Initialization of service bus
2. Connection request to target ECU
3. Response from body control ECU (for target ECU)
4. Communication request to target ECU
5. Gateway operation by body control ECU
6. Negative response from body control ECU
7. Response from target ECU
8. Gateway operation by body control ECU
Until a response is sent from the target ECU, the body
control ECU continues to send a negative response to
the service tool, enabling the tool to wait for a response
from the target ECU. Time-out process has been added
to each step of the procedure, to prevent locking in the
case of failure of any equipment.

Figure 10. An Example of Construction between Vehicle
and Dealer-installed Option LAN
BEAN has been adopted as the communication protocol
for the dealer-installed option LAN, as well as for the
body control system LAN. Basic gateway operation is as
follows.
Gateway from the body control system LAN to the dealerinstalled option LAN
1. Dealer-installed option bus buffer receives the BEAN
frame format from the body control system LAN.
2. After changing the destination ID of the BEAN frame
format, the bus buffer transmits the format to the
dealer-installed option LAN.
Gateway from the dealer-installed option LAN to the body
control system LAN
1. Dealer-installed option bus buffer receives the BEAN
frame format from the dealer-installed option LAN.
2. The BEAN frame format undergoes a security check.
3. The frame is reorganized.

Figure 9. Operation Sequence

4. The reorganized frame is transmitted to the body
control system LAN.

The gateway function for diagnostic tools has been realized by the above-mentioned method.

Figure 11 shows an example frame conversion.

SPECIFICATION OF GATEWAY BETWEEN DEALERINSTALLED OPTION LAN AND BODY CONTROL
SYSTEM LAN
Method of connecting the bus of dealer-installed options –
This section describes the method of connecting dealerinstalled options to the in-vehicle LAN. Figure 10 shows
the construction in-vehicle the dealer-installed option
LAN connected with the body control system LAN via the
gateway function. We call midget ECU that mounted
gateway function for connecting dealer-installed options
”bus buffer”.
Figure 11. An Example of Frame Conversion
The gateway between the body control system LAN and
the dealer-installed option LAN is designed such that it
can deal with relatively high traffic volume, providing for
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EFFECT OF GATEWAY BETWEEN ENTERTAINMENT
LAN AND BODY CONTROL SYSTEM LAN – The utility
of gateway between entertainment LAN and body control
system LAN, but in Figure 13 shows only one example of
applying to multi-display, is expected expanding, for
example, interactive control of navigation system and
engine and using speed-data from instrument-panelcluster to navigation system and audio control.

future expansion of dealer-installed options. When each
LAN has heavy traffic, frames to be transmitted may
remain in each bus buffer. A communication data buffer
is necessary to prevent the remaining frames from being
lost.
Adoption of communication data buffer – Investigation
revealed that, in data transmission from the body control
system LAN to the dealer-installed option LAN, the number of frames remaining in the bus buffer becomes the
largest when a combination of successive long and short
frames occurs as shown below.

EFFECT OF GATEWAY BETWEEN SERVICE LAN AND
BODY CONTROL SYSTEM LAN – Figure 14 shows the
result of a number of ECU can be diagnosed, in which
compared after introduction of gateway between service
LAN and body control system LAN with before.

Figure 12. Data Flow in Bus-Buffer
Based on this finding, it has been determined that any
dealer-installed option requires six stages of bus buffer.

EFFECT OF GATEWAY

Figure 14. Number of ECUs Communicating with
Diagnostic Tools

VEHICLE SYSTEM CONFIGURATION – Figure
13
shows an example application of the above-mentioned
gateway functions to an actual vehicle.

By the introduction of the gateway between ISO 9141based LANs and the body control system LAN(BEAN),
10 ECUs can be indirectly connected to the diagnostic
tool. As a result, the number of ECUs can be diagnosed
has increased by 8.
By implementing the relay function between ISO 9141based LANs and the body control system LAN (BEAN),
the following functional enhancement has been achieved
easily.
Changeable shipment information on-board – By using
the diagnosis connector installed in a completely assembled vehicle, it is possible to set each ECU connected
with the LAN memorizing shipment information, from the
facility in the vehicle assembly line. This feature is useful
to minimize parts numbers of ECUs.
According to this shipment information ECUs connected
to the LAN can behave properly in accordance with destinations it has shipped.

Figure 13. An Example of System Configuration
Gateway function between entertainment LAN and body
control system LAN is mounted multi-display ECU. Gateway function between service LAN and body control system LAN is mounted body-ECU-No.1. Gateway function
between dealer-installed option LAN and body control
system LAN is mounted bus buffer.

Settings at dealers in accordance with customers’
requests (Customize function) – With a service tool connected to a diagnosis connector linked to ISO 9141based LANs, if ECUs are set memorizing customized
information in accordance with customers’ requests. As a
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tion in short term with enormous development
expenditure.

result it is possible to change the sound volume of the
alarm buzzer, etc. and to add or remove optional functions.

3. It will be necessary to protect vehicle information
leakage and improve fail-safe capability depend on
outside bus connection, i.e. ITS bus, and enhancement of communication information. We will expand
gateway function more in order to establish firewall
function and security function.

These features can be added to all ECUs connected to
the LAN if gateway functions are mounted.
EFFECT OF GATEWAY BETWEEN A DEALERINSTALLED OPTION LAN AND BODY CONTROL
SYSTEM LAN – By the gateway between dealer-installed
option LAN and body control system LAN, we could
reduce the wire-harness and wiring work for installation
of a remote-engine-starter.

CONCLUSION
Gateway functions that exchange data among three independent LAN which are body control, entertainment control and diagnostics system has been developed. This
function makes easier for ECUs to adopt LAN communication with saving cost increase to avoid each ECU connects to plural communication bus, while ECU numbers
are increased which are connect to different LAN system.
The method for data communication on body control LAN
to outside through gateway function has also been developed. This method has brought after market products to
reduce installation workload at dealer with maintaining
the same fail-safe capability as before installation.

VARIATE OF GATEWAY DATA – The following diagram
shows gateway data among entertainment LAN, dealerinstalled option LAN and body control system LAN.

These gateway function has realized whole vehicle network system which effectively applies the each network
merit and adopt own strategy for each system.

ACKNOWLEDGMENTS
The authors would like to thank the members of the
BEAN developing activity for their valuable assistance
and cooperation.
Figure 15. Gateway Data Volume

REFERENCES

There are 319 kinds of data in body control system LAN.
Gateway data are 45 kind of entertainment LAN data and
54 kind of dealer-installed option LAN data.

1. Hiroshi Honda, Shigeru Uehara, Kazunori Sakai, Takao
Akatsuka, Susumu Akiyama, “Body Electronics Area Network(BEAN)”, SAE paper 970297

FUTURE TASKS
1. It is anticipated that gateway function handling ECUs
number will be increased with LAN application
expansion. And the processing load of ECU for communication becomes higher according to the incresed communication data. It is predictable that an
exclusive gateway function ECU could be required to
develop to apply for valiant vehicles as it is possible
to save software and hardware development cost on
the conventional ECU to additionally add on. Thus
exclusive ECU could be achieved both high reliability
and cost reduction by the drastic IC customization.
2. Although vehicle manufacturers adopted their own
protocols for LAN, these are standardizing step by
step. It is recommended to improve the automotive
electronics system architecture by degree with gateway function adoption to avoid the protocol modifica-

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