Bronkhorst DeviceNet slave interface Manuel d'utilisateur télécharger pdf (Page 19)

BRONKHORST®

Page19DeviceNetinterface   9.17.026

3.4 POLLEDI/O

3.4.1 Representation

AlloftheaboveattributesinthetablesfromTable2 ‐1toTable2‐16canbeaccessedusingExplicitMessaging.Upon

existenceofanexplicitconnection,aPolledI/Oconnectioncan also beestablished andcoexist. OncethePolled I/ O 

connectionhasbeenestablished,thedevicewillbeable

toacceptandprocessthePolledI/Orequests.Forexample,if

Instance#7hasbeenselectedasOutputIOAssemblyInstance,twodatabytesrepresentingthenewsetpointshallbe

appended to the Polled I/O request for setting a setpoint. If the Data Unit attribute were 0x1001 as the code

for

“Counts”,thevalueofthesetpointbyteswillbeansignedintegerwhere0x7D00(*)represents100%flowand0x0000

represents0%flow.UponreceptionofthePolledI/ORequest,ifInstance#2hasbeenselectedasInputIOAssembly

Instance the DeviceNet MFC will respond with a PolledI/O

 Response carrying with it three data bytes as described

below:

PolledI/OResponse’sDataFieldusingCountsasDataUnit

Byte0:

ExceptionStatus

Byte1:

IndicatedFlow(LSB)

Byte2:

IndicatedFlow(MSB)

BYTE INT(0x7D00=100%)



PolledI/ORequest’sDataFieldusingCountsasDataUnit

Byte0:

NewSetpoint(LSB)

Byte1:

NewSetpoint(MSB)

INT(0x7D00=100%)

Notethatif“Counts”hasbeenselectedfortheDataUnitattributeoftheAnalogSensorandControllerobject(i.e.,the

value of these attributes is 0x1001), then the Indicated‐Flow bytes in the Polled I/O Response represent the same

informationasthatoftheNew‐Setpointbytesinthe

PolledI/ORequest(i.e.,0x0000represents0%flowand0x7D00

(*)represents100%flow).However,ifthe“DataUnit”attributeoftheSensorandtheSetpointobjectare0x1400,the

valueoftheindicatedflowandsetpointwillbeinStandardCubicCentimeter(SCCM).Notethatthesetpointandthe

indicated

flowcanbesetwithdifferentdataunit(i.e.,CountsforSetpointandSCCMforIndicated‐floworviceversa).

SincetheIndicated‐flowandSetpointattributeareinteger,ifusedinSCCMmodethevalueoftheseattributecannot

exceed32767SCCM.ThereforetheSCCMmodeshallnot

beusedforMFCshavinggaseswiththefull‐scaleexceeding

32767SCCMorhavingtheFull‐scaleloadedwithSLMdataunit.

PolledI/OResponse’sDataFieldusingSCCMasDataUnit

Byte0:

ExceptionStatus

Byte1:

IndicatedFlow(LSB)

Byte2:

IndicatedFlow(MSB)

BYTE INT(0toFullScale)



PolledI/ORequest’sDataFieldusingSCCMasDataUnit

Byte0:

NewSetpoint(LSB)

Byte1:

NewSetpoint(MSB)

INT(0toFullScale)

Thetables above show some examples of the PolledI/Osetting. There areeight (8) IOAssembly Instances thatthe

usercanchoosefrom;4forinputand4foroutput.TheseinstancesarespecifiedintheMFCDeviceProfiledocument.

Seenextparagraphformoredetails.



(*)100%MeasuredValueindicationforBronkhorst instrumentsis0x7D00(signedinteger).Maximum

value for Measured Value is 102.4 %, which is: 0x7FFF. Other suppliers may use different ranges for

MeasuredValue.ViaFullScale: attribute 0x0A ofobject0x31,analogsensor, itispossible to readout

thesignedintegervalue

usedfor100%.



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Bronkhorst DeviceNet slave interface Manuel d'utilisateur Page 19

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