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General

Protocol & Address Issues

Solve common problems with protocol addresses, data types, and byte ordering.

This guide covers the most common user issues: protocol address formats and data type mismatches.

Quick Diagnostic

If you're getting incorrect or missing values, check these first:

SymptomLikely CauseJump To
All values are 0Wrong address formatAddress Syntax
Huge/tiny numbers (e.g., 1.234e+38)Byte order mismatchByte Ordering
Negative when expecting positiveSigned vs unsigned typeData Type Mismatch
Random-looking valuesWrong data type sizeData Type Mismatch
"Invalid address" errorSyntax errorAddress Syntax
Timeout errorsConnection issueGateway Not Connecting

Address Syntax by Protocol

Modbus TCP

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Most Common Mistake

Forgetting to subtract 1 from datasheet addresses. Modbus uses 0-based addressing!

Datasheet SaysFunction CodeProxus Address
40001FC03 (Holding Register)x=3;0
40100FC03 (Holding Register)x=3;99
30001FC04 (Input Register)x=4;0
30050FC04 (Input Register)x=4;49
00001FC01 (Coil)x=1;0
10001FC02 (Discrete Input)x=2;0

Conversion Formula:

Proxus Address = Datasheet Address - Base - 1

40001 series → Base = 40000, x=3
30001 series → Base = 30000, x=4

Example: Device manual says "Speed at register 40201"

  • Subtract 40000 → 201
  • Subtract 1 (0-based) → 200
  • Result: x=3;200

Siemens S7

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Most Common Mistake

Using Word offset instead of Byte offset. Siemens uses byte-based addressing!

TIA Portal ShowsProxus AddressData Type
DB1.DBX0.0DB1.0.0Bool
DB1.DBB10DB1.10Byte
DB1.DBW10DB1.10Short/UShort
DB1.DBD10DB1.10Int/Float
M0.0M0.0Bool
MW100MW100Short
I0.0I0.0Bool
Q0.0Q0.0Bool

Common Errors:

WrongCorrectIssue
DB1.DBD0DB1.0Remove DBD prefix, just use offset
DB1.W10DB1.10Use byte offset, set type to Short
DB1.10.8DB1.11.0Bits are 0-7, use next byte for bit 8

OPC UA

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Most Common Mistake

Forgetting the namespace index (ns=).

FormatExample
String NodeIdns=2;s=Channel1.Device1.Tag1
Numeric NodeIdns=3;i=1001
Hierarchicalns=2;s=PLC/Temperature

Tip: Use UaExpert to browse the server and copy exact Node IDs.

Allen-Bradley

Address TypeFormatExample
Tag NameDirect nameProgram:MainProgram.MyTag
Array Element[index]MyArray[5]
UDT Member.memberMotor1.Speed

Data Type Mismatch

Common Symptoms & Fixes

SymptomCauseSolution
Value is half/double expectedWrong type size (16 vs 32-bit)Change Short ↔ Int
Negative when should be positiveSigned vs UnsignedUse UShort instead of Short
Decimal missing (10.5 shows as 105)Integer instead of FloatChange to Float
Very large numbers (3.4e+38)Int read as FloatChange Float to Int
Value stuck at 65535 or -32768Overflow from wrong typeUse Int instead of Short

Type Size Reference

Proxus TypeSizeValue Range
Bool1 bittrue/false
Byte8 bit0 to 255
Short16 bit-32,768 to 32,767
UShort16 bit0 to 65,535
Int32 bit-2.1 billion to 2.1 billion
UInt32 bit0 to 4.3 billion
Float32 bit±3.4e38 (7 digits precision)
Double64 bit±1.7e308 (15 digits precision)

Modbus Register Count

TypeRegisters Used
Short/UShort1 register (16 bit)
Int/UInt/Float2 registers (32 bit)
Long/Double4 registers (64 bit)
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Check the Manual

Device manuals usually specify "2 registers" or "32-bit" for values. Match this with your Proxus type.

Byte Ordering Issues

Multi-byte values (Int, Float, Double) can be stored in different byte orders depending on the device manufacturer.

Symptoms of Wrong Byte Order

  • Float values are extremely large (e.g., 1.234e+38) or tiny (1.4e-45)
  • Integer values are nonsensical (e.g., 16777216 instead of 1)
  • Values change wildly with small actual changes

Byte Order Options

SettingNameByte SequenceCommon Devices
ABCDBig Endian12 34 56 78Most PLCs, Siemens
DCBALittle Endian78 56 34 12Some sensors
BADCMid-Big34 12 78 56Some energy meters
CDABMid-Little56 78 12 34ABB, some VFDs

How to Find the Right Setting

  1. Read a known value (e.g., write 1.0 to a register)
  2. If Proxus shows wrong value, try each byte order setting
  3. Test with distinctive values like 1234.5678 to verify

Setting Byte Order in Proxus

In the Device Profile connection parameters, set the DataFormat field:

  1. Open Data Management > Device Profiles
  2. Select your profile and go to Connection Parameters
  3. Set DataFormat to one of: ABCD, DCBA, BADC, or CDAB
info
Modbus TCP

For Modbus TCP devices, the DataFormat parameter is available directly in the connection settings. Other protocol-specific options like isStringReverse may also affect string byte ordering.

Protocol-Specific Errors

Modbus Errors

ErrorMeaningSolution
Illegal Function (01)Function code not supportedUse correct FC (x=1,2,3,4)
Illegal Data Address (02)Register doesn't existCheck register number in manual
Illegal Data Value (03)Value out of rangeCheck min/max for register
Gateway Path Unavailable (0A)Wrong Slave IDVerify Station parameter
TimeoutNo responseCheck IP, port, and network

Siemens S7 Errors

ErrorMeaningSolution
Connection refusedPUT/GET disabledEnable in TIA Portal
Address not foundDB doesn't existCreate DB or check number
Access deniedBlock protectedRemove protection in TIA
Invalid slotWrong rack/slotS7-300/400: Slot 2, S7-1200/1500: Slot 1

OPC UA Errors

ErrorMeaningSolution
BadNodeIdUnknownNode not foundVerify Node ID with UaExpert
BadCertificateUntrustedCertificate rejectedAdd to server's trusted folder
BadUserAccessDeniedWrong credentialsCheck username/password
BadSecurityModeRejectedSecurity mismatchMatch security mode with server

Error Code Reference

Below are the actual error codes you may encounter in Proxus logs. These codes indicate specific issues with PLC communication.

Modbus Error Codes

Error CodeMeaningSolution
ModbusCRCCheckFailedCRC checksum mismatchCheck wiring, baud rate, and parity settings
ModbusLRCCheckFailedLRC checksum mismatch (ASCII mode)Verify ASCII mode settings match device
ModbusAsciiFormatCheckFailedInvalid ASCII frame formatEnsure device uses Modbus ASCII protocol
ModbusTcpFunctionCodeNotSupportUnsupported function codeUse correct function code (FC01-04)
ModbusTcpFunctionCodeOverBoundRegister address out of rangeCheck address exists in device
ModbusBitIndexOverstepBit index 0-15 exceededUse valid bit index within word
ModbusAddressMustMoreThanOneInvalid starting addressAddress must be > 0 when offset is enabled

Siemens S7 Error Codes {#s7-errors}

Error CodeMeaningSolution
SiemensError000AObject does not existDB block not found; create in TIA Portal
SiemensDataLengthCheckFailedBlock length mismatchEnable PUT/GET; disable "Optimized block access"
SiemensReadLengthOverPlcAssignRead exceeds PLC limitReduce read length or split into multiple reads
SiemensReadLengthMustBeEvenNumberOdd byte lengthData length must be even for word types
SiemensDBAddressNotAllowedLargerThan255DB number > 255Use DB numbers 1-255 for S7-300/400
SiemensWriteErrorWrite operation failedCheck write permissions and address validity
SiemensError0006Unsupported data typeUse supported types (Bool, Int, Real, etc.)

Mitsubishi/Melsec Error Codes

Error CodeMeaningSolution
MelsecError02Invalid device rangeCheck device address exists in PLC
MelsecErrorC056Address exceeded maximumReduce address or use extended memory
MelsecErrorC05FTarget PLC rejected requestCheck network number and PC number
MelsecErrorC051_54Read/write points out of rangeReduce number of points per request
MelsecErrorC05ECommunication timeoutIncrease timeout or check network
MelsecFxCrcCheckFailedCRC check failedVerify serial settings (baud, parity)
MelsecFxReceiveZeroNo response from PLCCheck connection and PLC power
MelsecCurrentTypeNotSupportedBitOperateBit operation not supportedUse word device for this data type

Omron FINS Error Codes

Error CodeMeaningSolution
OmronStatus20Connection limit exceededReduce concurrent connections
OmronStatus21Node already connectedClose existing connection first
OmronStatus22Protected network nodeConfigure node in CX-Programmer
OmronStatus23Network node out of rangeUse valid node address (1-126)
OmronStatus24Node already in useChoose different node address
OmronStatus25All nodes in useFree up connections on network
OmronReceiveDataErrorData receive exceptionCheck FINS port (9600) and DA1/SA1

Allen-Bradley Error Codes

Error CodeMeaningSolution
IOI could not be decipheredTag path invalidVerify tag name and path syntax
Tag does not existTag not found in PLCCheck tag spelling in Studio 5000
Insufficient memoryResponse buffer overflowReduce read size or split requests
Forward Open failedCIP connection rejectedCheck slot, IP, and connection limits

Panasonic Mewtocol Error Codes

Error CodeMeaningSolution
PanasonicMewStatus40BCC error (checksum)Check serial cable and wiring
PanasonicMewStatus41WACK error - buffer fullReduce request frequency
PanasonicMewStatus60Parameter errorCheck command format and values
PanasonicMewStatus61Data error - BCD overflowVerify data format (BCD/HEX)
PanasonicMewStatus63PLC mode errorSwitch PLC to correct mode
PanasonicMewStatus65Protection errorDisable write protection

Keyence Error Codes

Error CodeMeaningSolution
KeyenceNanoE0Device/address out of rangeCheck device number and bank
KeyenceNanoE1Command not supportedUse supported CPU commands
KeyenceSR2000Error00Undefined commandCheck command format
KeyenceSR2000Error20Current mode errorSwitch to appropriate mode
KeyenceSR2000Error21Buffer fullWait and retry operation
Error CodeMeaningSolution
YokogawaLinkError01CPU number out of rangeUse CPU 1-4
YokogawaLinkError02Command does not existCheck command spelling
YokogawaLinkError03Device name does not existVerify device in program
YokogawaLinkError42Checksum differsCheck cable and connections
YokogawaLinkError44Timeout receivingIncrease timeout; check wiring

Beckhoff ADS Error Codes

Error CodeMeaningSolution
ADS Error 1793Service not supportedCheck TwinCAT version
ADS Error 1808Symbol not foundVerify variable name in PLC
Target machine not foundNo route to targetCheck AmsNetId and route
Symbol download requiredTPY file outdatedRe-download symbols

Delta DVP Error Codes

Error CodeMeaningSolution
Illegal addressAddress not validCheck device memory map
Receive check failedChecksum errorVerify serial settings
Response format errorInvalid responseCheck protocol mode

XINJE Error Codes

Error CodeMeaningSolution
Address format errorInvalid address syntaxUse correct format (D100, M0)
Protocol type errorWrong protocol modeMatch protocol to PLC series

GE SRTP Error Codes

Error CodeMeaningSolution
Not support bit read/writeBit operations blockedUse word operations
Address cannot be 0Invalid starting addressStart from address 1
Length must be evenOdd byte countUse even byte lengths

Fuji SPB Error Codes

Error CodeMeaningSolution
FujiSpbStatus01Write to ROM attemptedCheck memory area
FujiSpbStatus02Undefined commandVerify command format
FujiSpbStatus03Data contradictionCheck parameter values

LSIS Error Codes

Error CodeMeaningSolution
LsisCnet0003Blocks exceed 16Split into smaller requests
LsisCnet1232Max 60 words exceededReduce words per request
LsisCnet0007Invalid data typeUse X, B, W, D, or L types

YASKAWA YRC Robot Error Codes

Error CodeMeaningSolution
YRC1010Command exceptionCheck command syntax
YRC2120Data cannot be readVerify variable access
YRC3010Servo power offEnable servo power
YRC5110Syntax errorCheck command format
Robot in actionRobot busyWait for motion complete
Hold is stoppingIn hold stateRelease hold signal

Fanuc CNC Error Codes

Error CodeMeaningSolution
Protocol errorCommunication failureCheck FOCAS library
Invalid parameterParameter out of rangeVerify parameter values
CNC not readyMachine busyWait for ready state

Kuka Robot Error Codes

Error CodeMeaningSolution
Variable not foundKRL variable missingCreate variable in program
Robot not readyNot in correct modeSwitch to EXT/AUTO mode
Program errorSubmit errorCheck KRL syntax

General Connection Errors

Error CodeMeaningSolution
ConnectTimeoutConnection timed outCheck IP, port, and firewall settings
ReceiveDataTimeoutNo response receivedIncrease timeout; check device is responding
ConnectionIsNotAvailableConnection droppedNetwork issue; will auto-reconnect
SocketContentReceiveExceptionSocket receive errorCheck network stability
IpAddressErrorInvalid IP formatUse format: 192.168.1.100
Remote host forcibly closedDevice disconnectedCheck device power and cables
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Finding Error Codes

Filter system logs by Category = Proxus.ProtocolDrivers to see protocol-specific errors with full context. Original error details are always preserved in the log message.

Validation Tools

Use Device Simulators

Before connecting to real hardware, test with simulators:

Use Protocol Analyzers

  • UaExpert (OPC UA) - Browse, read, write nodes
  • Modbus Poll - Test Modbus communication
  • Wireshark - Capture and analyze network traffic

See Also

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