
APPLICATIONNOTEAN‐BEI‐P2‐038 Date:15/02/12
AN‐BEI‐P2‐038ModbusRTUControlandRegisterMapping
15
ModbusExceptionResponseTelegrams
Undersomecircumstances,thedrivemayreplywithanExceptionResponse(error)inresponsetoarequesttelegramsentfrom
thenetworkmaster,forexamplewherethemastertriestoreadaregisterwhichdoesnotexist.ExceptionResponseswhichcan
begeneratedbythedrive
arelistedbelow:‐
ExceptionCode1:InvalidRequest
Returnedunderthefollowingconditions
• NetworkMastersendsanunsupportedModbuscommand(e.g.ReadCoils).
• RuncommandissuedtodrivewhilstthedriveisnotsetforModbusControlMode(e.g.P1‐12<>4).
• Runcommandissuedto
driveswhilstthedriveisnotenabled(e.g.DigitalInput1isopen).
• Runcommandissuedtodrivewhilstthedriveisinatrippedcondition.
ExceptionCode2:InvalidModbusregister
Returnedunderthefollowingconditions
• NetworkMasterattemptstoreadorwritearegisterthatdoes
notexistwithinthedrive.
ExceptionCode3:RegisterValueOutofRange
Returnedunderthefollowingconditions
• NetworkMasterattemptstowriteaholdingregisterwithavalueoutsidetherangeoftheregister
ExceptionCode6:DriveBusy
Returnedunderthefollowingconditions
• Drivebusydue
tointernaldatatransfer.TheNetworkMastershouldre‐sendthemessageafteradelay
Dataflowexample:
Readdatafromregister6:
Request:[01] [03][00][05] [00][01][94][0B]
(DriveAddr)(Command)(Regstartaddr)(No.ofRegisters)(Checksum)
Reply:[01] [03][02] [00][00][B8]
[44]
(DriveAddr)(Command)(Noofdatabytes)(Data) (Checksum)
Note:Theactualstartaddressofregister6is5.Alldatain[]isin8bitsHexformat.
Writestartcommandtotheregister1(supposeP1‐12=4,P1‐13=1anddigitalinput1
isclosed):
Request: [01] [06] [00][00] [00][01] [48][0A]
(DriveAddr) (Command) (Regaddr) (Datavalue) (Checksum)
Reply: [01] [06] [00][00] [00][01] [48][0A]
(DriveAddr) (Command) (Regaddr) (Datavalue) (Checksum)
Note:Theactualaddressofregister1onthedatalinkis0.
Alldatain[]isin8bitsHexformat.
Replycanbeerrormessagedependingondriveparametersettingsanddigitalinputstatus.
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