ProgrammingGuide
MarathonSeriesFA/FR 39
9ProgrammingGuide
Thissectionexplainsthesensor’scommunicationprotocol.Usethemwhenwritingcustomprograms
foryourapplicationsorwhencommunicatingwithyoursensorwithaterminalprogram.
9.1RemoteversusManualConsiderations
Since the sensor includes a local user interface, the possibility exists for a person to make manual
changes to parameter settings. To resolve conflicts between inputs to the sensor, it observes the
followingrules:
• Commandprecedence:the mostrecentparameterchangeisvalid,whetheroriginatingfrom
manualorremote.
• If
amanualparameterchangeismade,thesensorwilltransmita“notification”stringtothe
host.(Notificationstringsaresuppressedinmultidropmode.)
• Amanuallockoutcommandisavailableintheprotocolssetsothehostcanrendertheuser
interface“displayonly,”ifdesired.
Allparameterssetviathe
2‐wayinterfaceareretainedinthesensor’snonvolatilememory.
When a unit is placed in multidrop mode its manual user interface is 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 outside the allowed range, an appropriate “error” response
character shall be
transmittedbackbythesensor.
All commands must be entered in upper case (capital) letters. Also note that leading
andtrailingzerosarenecessary!
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