Yokogawa RotaMASS 3-Series Uživatelský manuál stáhnout pdf (Strana 13)

IM 01R04B08-00E-E 1st edition February 15, 2012 -00

<3. ABOUT MODBUS>

3-1

3. ABOUT MODBUS

3.1 Outline

MODBUSisabi-directionaldigitalcommunicationprotocolalsoforelddevices,whichoffersan

advancementincommunicationspeedandiswidelyemployedbynumerouselddevices.

TheMODBUScommunicationtypeoftheRotamassemploysthespecicationstandardizedbythe

MODBUSOrganization,andprovidesinteroperabilitywithdevicesproducedbyothermanufacturers.

Featuringtransmissionofallmeasurementvariablesandunitsasinputregistersandotherparametersas

holding registers, the MODBUS communication type’s software enables a exible instrumentation system to

be implemented.

For information on other features, engineering, design, construction work, startup and maintenance of

MODBUS,refertotheModbusOrganization(www.modbus.org).

3.2 Wiring System Conguration

Thenumberofdevicesthatcanbeconnectedtoasinglebuswithoutrepeateris32.Themaximumcable

length depends on baud rate, cable properties and network conguration. When constructing systems, both

thebasicandoveralldesignmustbecarefullyconsideredtoallowdeviceperformancetobefullyexhibited.

ThefollowinginstrumentsarerequiredforusewithMODBUSdevices:

• Terminator:

MODBUS requires two terminators at the ends of the trunk line. Refer to the supplier for details of

terminators.

• Field devices:

ConnectyourMODBUScommunicationtypeROTAMASS3SeriestoaMODBUS.OneormoreROTAMASS

3Seriesandotherelddevicescanbeconnected.FortheterminalassignmentontheROTAMASS3

Series, see chapter 4.1.

• Host:

Usedforaccessingelddevices.Adedicatedhost(suchasDCS)isusedforaninstrumentationlinewhile

dedicated communication tools are used for startup or maintenance. For operation of the host, refer to the

instructionmanualforeachhost.Nodetailsofthehostareexplainedintherestofthismanual.

• Cable:

Usedforconnectingdevices.Refertohttp://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf for

details of instrumentation cabling. If the total length of the cable is in a range of 2 to 3 meters for laboratory

or other experimental use, the following simplied cable (a twisted pair wire with a cross section of 0.9 mm² or

more and cycle period of within 5 cm (2 inches) may be used). Termination processing depends on the type

ofdevicebeingdeployed.FortheROTAMASS,clampterminalareused.

ConnectthedevicesasshowninFigure3.1.Connecttheterminatorsatbothendsofthetrunk,witha

minimum length of the spur for connection.

The polarity of signal must be maintained.

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Yokogawa RotaMASS 3-Series Uživatelský manuál Strana 13