Forgetting to subtract 1 from datasheet addresses. Modbus uses 0-based addressing.
Datasheet Says
Function Code
Proxus Address
40001
FC03 (Holding Register)
x=3;0
40100
FC03 (Holding Register)
x=3;99
30001
FC04 (Input Register)
x=4;0
30050
FC04 (Input Register)
x=4;49
00001
FC01 (Coil)
x=1;0
10001
FC02 (Discrete Input)
x=2;0
Conversion Formula:
Proxus Address = Datasheet Address - Base - 140001 series → Base = 40000, x=330001 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
warning
Most Common Mistake
Using Word offset instead of Byte offset. Siemens uses byte-based addressing!
TIA Portal Shows
Proxus Address
Data Type
DB1.DBX0.0
DB1.0.0
Bool
DB1.DBB10
DB1.10
Byte
DB1.DBW10
DB1.10
Short/UShort
DB1.DBD10
DB1.10
Int/Float
M0.0
M0.0
Bool
MW100
MW100
Short
I0.0
I0.0
Bool
Q0.0
Q0.0
Bool
Common Errors:
Wrong
Correct
Issue
DB1.DBD0
DB1.0
Remove DBD prefix, just use offset
DB1.W10
DB1.10
Use byte offset, set type to Short
DB1.10.8
DB1.11.0
Bits are 0-7, use next byte for bit 8
OPC UA
warning
Most Common Mistake
Forgetting the namespace index (ns=).
Format
Example
String NodeId
ns=2;s=Channel1.Device1.Tag1
Numeric NodeId
ns=3;i=1001
Hierarchical
ns=2;s=PLC/Temperature
Tip: Use UaExpert to browse and copy the correct Node IDs.
MTConnect
warning
Most Common Mistake
Using an incomplete Host endpoint (missing scheme/port) or selecting a gateway that cannot reach the machine network.
Item
Format
Example
Host
http://<ip>:<port>
http://192.168.1.20:5000
Tag Address
<DeviceName>/<ComponentPath>/<DataItemId>
Mazak-01/Controller/exec
Root-level Tag
<DeviceName>/<DataItemId>
Mazak-01/avail
Common Errors:
Wrong
Correct
Issue
192.168.1.20
http://192.168.1.20:5000
Missing explicit endpoint details
Mazak-01\\Controller\\exec
Mazak-01/Controller/exec
Use / separators
Mazak_01/Controller/exec
Mazak-01/Controller/exec
Device name must match MTConnect device name exactly
Allen-Bradley
Address Type
Format
Example
Tag Name
Direct name
Program:MainProgram.MyTag
Array Element
[index]
MyArray[5]
UDT Member
.member
Motor1.Speed
Data Type Mismatch
Common Symptoms & Fixes
Symptom
Cause
Solution
Value is half/double expected
Wrong type size (16 vs 32-bit)
Change Short ↔ Int
Negative when should be positive
Signed vs Unsigned
Use UShort instead of Short
Decimal missing (10.5 shows as 105)
Integer instead of Float
Change to Float
Very large numbers (3.4e+38)
Int read as Float
Change Float to Int
Value stuck at 65535 or -32768
Overflow from wrong type
Use Int instead of Short
Type Size Reference
Proxus Type
Size
Value Range
Bool
1 bit
true/false
Byte
8 bit
0 to 255
Short
16 bit
-32,768 to 32,767
UShort
16 bit
0 to 65,535
Int
32 bit
-2.1 billion to 2.1 billion
UInt
32 bit
0 to 4.3 billion
Float
32 bit
±3.4e38 (7 digits precision)
Double
64 bit
±1.7e308 (15 digits precision)
Modbus Register Count
Type
Registers Used
Short/UShort
1 register (16 bit)
Int/UInt/Float
2 registers (32 bit)
Long/Double
4 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
Setting
Name
Byte Sequence
Common Devices
ABCD
Big Endian
12 34 56 78
Most PLCs, Siemens
DCBA
Little Endian
78 56 34 12
Some sensors
BADC
Mid-Big
34 12 78 56
Some energy meters
CDAB
Mid-Little
56 78 12 34
ABB, some VFDs
How to Find the Right Setting
Read a known value (e.g., write 1.0 to a register)
If Proxus shows wrong value, try each byte order setting
Test with distinctive values like 1234.5678 to verify
Setting Byte Order in Proxus
In the Device Profile connection parameters, set the DataFormat field:
Open Data Management > Device Profiles
Select your profile and go to Connection Parameters
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.
Security mode/policy not supported or certificate untrusted
Verify the mode+policy combination matches what the server offers; trust the client certificate
BadNodeIdUnknown
Node not found
Verify Node ID with UaExpert
BadCertificateUntrusted
Certificate rejected
Add to server's trusted folder
BadUserAccessDenied
Wrong credentials
Check username/password
BadSecurityModeRejected
Security mismatch
Match security mode with server
MTConnect Errors
Error / Symptom
Meaning
Solution
No devices found
Probe returned empty or unreachable endpoint
Verify MTConnect Agent URL and check endpoint from selected gateway network
Unknown address
Selected tag path no longer exists in current MTConnect model
Re-open browser and re-select tags from current hierarchy
Frequent UNAVAILABLE
Data item currently not published/available
Validate machine state and data item availability in agent output
Browser works on one gateway but not another
Network segmentation / firewall between gateway and machine
Use a gateway in the same machine network zone
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 Code
Meaning
Solution
ModbusCRCCheckFailed
CRC checksum mismatch
Check wiring, baud rate, and parity settings
ModbusLRCCheckFailed
LRC checksum mismatch (ASCII mode)
Verify ASCII mode settings match device
ModbusAsciiFormatCheckFailed
Invalid ASCII frame format
Ensure device uses Modbus ASCII protocol
ModbusTcpFunctionCodeNotSupport
Unsupported function code
Use correct function code (FC01-04)
ModbusTcpFunctionCodeOverBound
Register address out of range
Check address exists in device
ModbusBitIndexOverstep
Bit index 0-15 exceeded
Use valid bit index within word
ModbusAddressMustMoreThanOne
Invalid starting address
Address must be > 0 when offset is enabled
Siemens S7 Error Codes {#s7-errors}
Error Code
Meaning
Solution
SiemensError000A
Object does not exist
DB block not found; create in TIA Portal
SiemensDataLengthCheckFailed
Block length mismatch
Enable PUT/GET; disable "Optimized block access"
SiemensReadLengthOverPlcAssign
Read exceeds PLC limit
Reduce read length or split into multiple reads
SiemensReadLengthMustBeEvenNumber
Odd byte length
Data length must be even for word types
SiemensDBAddressNotAllowedLargerThan255
DB number > 255
Use DB numbers 1-255 for S7-300/400
SiemensWriteError
Write operation failed
Check write permissions and address validity
SiemensError0006
Unsupported data type
Use supported types (Bool, Int, Real, etc.)
Mitsubishi/Melsec Error Codes
Error Code
Meaning
Solution
MelsecError02
Invalid device range
Check device address exists in PLC
MelsecErrorC056
Address exceeded maximum
Reduce address or use extended memory
MelsecErrorC05F
Target PLC rejected request
Check network number and PC number
MelsecErrorC051_54
Read/write points out of range
Reduce number of points per request
MelsecErrorC05E
Communication timeout
Increase timeout or check network
MelsecFxCrcCheckFailed
CRC check failed
Verify serial settings (baud, parity)
MelsecFxReceiveZero
No response from PLC
Check connection and PLC power
MelsecCurrentTypeNotSupportedBitOperate
Bit operation not supported
Use word device for this data type
Omron FINS Error Codes
Error Code
Meaning
Solution
OmronStatus20
Connection limit exceeded
Reduce concurrent connections
OmronStatus21
Node already connected
Close existing connection first
OmronStatus22
Protected network node
Configure node in CX-Programmer
OmronStatus23
Network node out of range
Use valid node address (1-126)
OmronStatus24
Node already in use
Choose different node address
OmronStatus25
All nodes in use
Free up connections on network
OmronReceiveDataError
Data receive exception
Check FINS port (9600) and DA1/SA1
Allen-Bradley Error Codes
Error Code
Meaning
Solution
IOI could not be deciphered
Tag path invalid
Verify tag name and path syntax
Tag does not exist
Tag not found in PLC
Check tag spelling in Studio 5000
Insufficient memory
Response buffer overflow
Reduce read size or split requests
Forward Open failed
CIP connection rejected
Check slot, IP, and connection limits
Panasonic Mewtocol Error Codes
Error Code
Meaning
Solution
PanasonicMewStatus40
BCC error (checksum)
Check serial cable and wiring
PanasonicMewStatus41
WACK error - buffer full
Reduce request frequency
PanasonicMewStatus60
Parameter error
Check command format and values
PanasonicMewStatus61
Data error - BCD overflow
Verify data format (BCD/HEX)
PanasonicMewStatus63
PLC mode error
Switch PLC to correct mode
PanasonicMewStatus65
Protection error
Disable write protection
Keyence Error Codes
Error Code
Meaning
Solution
KeyenceNanoE0
Device/address out of range
Check device number and bank
KeyenceNanoE1
Command not supported
Use supported CPU commands
KeyenceSR2000Error00
Undefined command
Check command format
KeyenceSR2000Error20
Current mode error
Switch to appropriate mode
KeyenceSR2000Error21
Buffer full
Wait and retry operation
Yokogawa Link Error Codes
Error Code
Meaning
Solution
YokogawaLinkError01
CPU number out of range
Use CPU 1-4
YokogawaLinkError02
Command does not exist
Check command spelling
YokogawaLinkError03
Device name does not exist
Verify device in program
YokogawaLinkError42
Checksum differs
Check cable and connections
YokogawaLinkError44
Timeout receiving
Increase timeout; check wiring
Beckhoff ADS Error Codes
Error Code
Meaning
Solution
ADS Error 1793
Service not supported
Check TwinCAT version
ADS Error 1808
Symbol not found
Verify variable name in PLC
Target machine not found
No route to target
Check AmsNetId and route
Symbol download required
TPY file outdated
Re-download symbols
Delta DVP Error Codes
Error Code
Meaning
Solution
Illegal address
Address not valid
Check device memory map
Receive check failed
Checksum error
Verify serial settings
Response format error
Invalid response
Check protocol mode
XINJE Error Codes
Error Code
Meaning
Solution
Address format error
Invalid address syntax
Use correct format (D100, M0)
Protocol type error
Wrong protocol mode
Match protocol to PLC series
GE SRTP Error Codes
Error Code
Meaning
Solution
Not support bit read/write
Bit operations blocked
Use word operations
Address cannot be 0
Invalid starting address
Start from address 1
Length must be even
Odd byte count
Use even byte lengths
Fuji SPB Error Codes
Error Code
Meaning
Solution
FujiSpbStatus01
Write to ROM attempted
Check memory area
FujiSpbStatus02
Undefined command
Verify command format
FujiSpbStatus03
Data contradiction
Check parameter values
LSIS Error Codes
Error Code
Meaning
Solution
LsisCnet0003
Blocks exceed 16
Split into smaller requests
LsisCnet1232
Max 60 words exceeded
Reduce words per request
LsisCnet0007
Invalid data type
Use X, B, W, D, or L types
YASKAWA YRC Robot Error Codes
Error Code
Meaning
Solution
YRC1010
Command exception
Check command syntax
YRC2120
Data cannot be read
Verify variable access
YRC3010
Servo power off
Enable servo power
YRC5110
Syntax error
Check command format
Robot in action
Robot busy
Wait for motion complete
Hold is stopping
In hold state
Release hold signal
Fanuc CNC Error Codes
Error Code
Meaning
Solution
Protocol error
Communication failure
Check FOCAS library
Invalid parameter
Parameter out of range
Verify parameter values
CNC not ready
Machine busy
Wait for ready state
Kuka Robot Error Codes
Error Code
Meaning
Solution
Variable not found
KRL variable missing
Create variable in program
Robot not ready
Not in correct mode
Switch to EXT/AUTO mode
Program error
Submit error
Check KRL syntax
General Connection Errors
Error Code
Meaning
Solution
ConnectTimeout
Connection timed out
Check IP, port, and firewall settings
ReceiveDataTimeout
No response received
Increase timeout; check device is responding
ConnectionIsNotAvailable
Connection dropped
Network issue; will auto-reconnect
SocketContentReceiveException
Socket receive error
Check network stability
IpAddressError
Invalid IP format
Use format: 192.168.1.100
Remote host forcibly closed
Device disconnected
Check 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:
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