42 rt flex bus system

7/28/2019 42 RT Flex Bus System

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RT-flex Training

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Data Bus System

Wrtsil Land & Sea Academy 1 Chapter 42

Chapter 42


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RT-flex Bus Systems

There are many possibil ities to connect the various sensors,

control lers, switches, transmitters, actuators, etc.

Wrtsil Land & Sea Academy Page 2 Chapter 42


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RT-flex Bus Systems Traditional Cabling

Each element is connected to terminal boxes and controllers byindividual cables. Numberless cable trees with an endless potentialfor misconnections, broken wires, short circuits, etc.



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RT-flex Bus Systems Bus Connections

Sensor cables



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Bus elements so called nodes are communicatin ver fast bexchanging digital messages in a defined, Bus specific language

(so called protocol) over a two-wire cable. Different systems may.

In a Bus system all nodes are connected in series, one after theother. There are clearly defined two ends of each Bus.

Bus systems MUST NOT be connected in parallel as star-connection.



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Less cablin work with low risk of malfunctionin .

Bus systems are robust in electromagnetically noisy environments.

- .

At each end of the Bus cable, there must be a terminating resistor ofspecified resistance matched with the wave impedance of the Bus

cable.



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RT-flex Bus Systems Bus Systems

Bus s stems used for WECS-9520:

CANopen (System Bus and Module Bus)

SSI Bus



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RT-flex Bus Systems CAN Bus

CAN Bus

CAN (Controller Area Network) is a multicast shared, differential

serial bus standard, originally developed by Bosch for connectinge ec ronc con ro un s n e au omo ve n us ry.

CANopen is a standard CAN protocol for process control systemsaccordin to ISO 11898.

WECS-9520 uses two different CANopen Busses: System Bus andModule Bus. Each FCM-20 module has three CANopen interfaces.

The System Bus is used for the communication between FCM-20modules and is not leaving the rail unit box. There are two S-Buses

for redundanc reasons.

The Module Bus is connecting only one specific FCM-20 module tointernal or external devices.



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RT-flex Bus Systems CAN Bus Interface to PCS

Remote Control System

Crew Operator InterfaceAlarm System

Digital

Governor

Two modules are responsiblefor the communication withthe PCS, these are FCM-20

redundantCANopen Bus

dPSC

#1 and FCM2-20 #2.

Two modules are usedMMI ecause o e re un ancy.

There are 5 classes of

FCM 1 FCM 2 FCM 3 FCM 4 FCM 5

CAN CAN CAN CAN CAN

Commands from RCS

exchanged:

System CAN BUS (redundant)and Digital Governor

Feedback signals fromo an g aGovernor

Parameters and indications fromand to Crew Operator Interface


Safety System

arms o


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RT-flex Bus Systems Modbus

Modbus is a data transmission protocol for process control systems.It was develo ed b the com an Gould Modicon which namedtheir bus protocol by the company's name.

The basic function of the ModBus system is the same as with CAN

but using a different language.Each FCM-20 has one RS-485 interface used for ModBus connection

Alarm Monitoring System which required such protocol.

ModBus s stemis used for some Pro ulsion Control S stemandAMS.



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Else if, the execution fails or the data was faulty, the slave returns an .

The data transmission mode for the Modbus data is the RTU

[Remote Terminal Unit] mode. Possible is alsoASCII [AmericanStandard Code f. Information Interchange) mode like on a normalPC, but RTU is twice as fast as the ASCII and therefore default in themodbus rotocol.

The RTU coding format is 1 byte = 11bit,

z 1 start bit

z 8-bit binary for the data, least significant bit first, 2x 4bithexadecimal characters

therefore:)

z 2 stop bits (instead of 1 bit, because of no parity).



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A messa e normall contains more than one b te of data information.

The slaves recognize separate messages from each other by a silent

interval of a certain length between the different messages (orpackets).

Only the master addresses actions from the slave. Therefore the each,

require one.

In the WECS a lication alwa s the ro ulsion control or the alarmmonitoring system is the master.

The FCM-20 modules only work as slave and respond to requestsfromPCS orAMS. All FCM-20 modules have the hexadecimaladdress 11h.



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and flexView data from FCM-20 #3 and #4.

Both busses carry out exactly the same actions, i.e. the bus traffic isredundant.

The Propulsion Control System delivers all required maneuveringa a, ue comman , a a or manua con ro pane s an

safety system states to FCM-20 #1 and #2.



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RT-flex Bus Systems SSI Bus

SSI Bus

The SSI Bus is a very fast Bus system.

signals to FCM-20 modules (except the spare on line one).

The SSI Bus consist of two lines: Clock Bus and Data Bus.

Always the last and one before the last cylinder modules aregenerating Clock Pulses send over the Clock Bus to synchronizetransmission and rece tion of data trou h the Data Bus.

Termination resistors are required on the end of the Bus lines except

the E96 box (Crank Angle Encoders are equipped with built in.



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RT-flex Bus Systems Bus Telegram

The Bus message, the Bus Telegram, consist of the followinginformation:

SOF

1 bit

Arbi tration

12 bits

Control

6 bits

Data

1-64 bits

CRC

9 bits

Ackn.

2 bits

EOF

1 bits

The Telegram can not be read with normal instruments

.

Physical condition of the Bus can be assessed by oscilloscope.



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RT-flex Bus Systems Bus cabling

S ecial attention has to be ut on the Bus cablin .

Only special CAN or Bus cables may be used



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RT-flex Bus Systems Bus cabling

At each end of the Bus cable a

terminator resistor of 120 mustbe installed to avoid signalreflection.


42 rt flex bus system

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