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ProgrammingGuide
MarathonSeriesFA/FR 39
9ProgrammingGuide
Thissectionexplainsthesensor’scommunicationprotocol.Usethemwhenwritingcustomprograms
foryourapplicationsorwhencommunicatingwithyoursensorwithaterminalprogram.
9.1RemoteversusManualConsiderations
Since the sensor includesa localuserinterface, thepossibility existsfor aperson tomake manual
changes to parameter settings. To resolve conflicts between inputs to the sensor, it observes the
followingrules:
• Commandprecedence:themostrecentparameterchangeisvalid,whetheroriginatingfrom
manualorremote.
• If
amanualparameterchangeismade,thesensorwilltransmita“notification”stringtothe
host.(Notificationstringsaresuppressedinmultidropmode.)
• Amanuallockoutcommandisavailableintheprotocolssetsoth ehostcanrendertheuser
interface“displayonly,”ifdesired.
Allparameterssetviathe
2‐wayinterfaceareretainedinthesensor’snonvolatilememory.
Whena unit isplaced in multidropmode its manual user interfaceis automatically
locked! It can be unlocked with the command XXXJ=U <CR>, where XXX is the
multidropaddress.
9.2CommandStructure
Protocols are the set of commands that define all possible communications with the sensor. The
commands are described in the following sections along with their associated ASCII command
charactersandrelatedmessageformatinformation.Typesofcommandsincludethefollowing:
1. Arequestforthecurrentvalueofaparameter
2.
Achangeinthesettingofaparameter
3. Defining the information contents of a string (either continuously output or periodically
polledattheoptionoftheuser)
Thesensorwillrespondtoeverycommandwitheitheran“acknowledge”ora“notacknowledge”
string.Acknowledgestringsbeginwiththeexclamation
mark!andareeitherverificationofaset
commandoraparametervalue.
Iftheunitisinmultidropmodethe3‐digitaddresscanbesentout
beforetheexclamationmark.
Forachangeinthesettingofaparameter,therangeofpossiblesettingvaluesisdefined,and,ifthe
host inputs a value outsidethe allowed range, an appropriate “error” response
character shall be
transmittedbackbythesensor.
Allcommandsmust beenteredinuppercase (capital)letters.Also notethatleading
andtrailingzerosarenecessary!