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Endianness / Byte Swap Converter

Swap byte and word orders (Little Endian, Big Endian) to resolve register mismatch.

32-Bit Input

Provide exactly 8 hex characters (4 bytes).

41 48 00 00

Endianness Swaps

Big Endian (ABCD) 41480000
Float: 12.5 Int32: 1095237632
Little Endian (DCBA) 00004841
Float: 0.00 Int32: 18497
Byte Swap (BADC) 48410000
Float: 197632.0 Int32: 1212284928
Word Swap (CDAB) 00004148
Float: 0.00 Int32: 16712
info
Disclaimer of Liability: This calculator is provided for educational and estimation purposes only. By using this tool, you agree to discharge AutomationView of any liability for direct, indirect, or consequential damages resulting from its use. It is your strict responsibility to independently verify all calculations, validate the results against official manufacturer documentation, and ensure compliance with all applicable safety and engineering standards before implementing any parameters in a production environment.

Understanding Endianness in Industrial Networks

In the realm of industrial automation, endianness refers to the specific order in which bytes are arranged within multi-byte data types, such as 32-bit integers or floats, during memory storage or network transmission. Recognizing and managing endianness is crucial for seamless communication between disparate systems like PLCs, HMIs, and SCADA servers.

The Modbus Word Order Challenge

The Modbus protocol specification standardizes 16-bit registers using a Big-Endian format, meaning the most significant byte is transmitted first. However, Modbus does not dictate a standard for larger data types (like 32-bit REALs or DINTs). This ambiguity leads to four common byte and word permutations depending on the equipment manufacturer:

  • ABCD (Big-Endian): The standard sequential order.
  • BADC (Byte Swap): Swaps the bytes within each 16-bit word.
  • CDAB (Word Swap): Swaps the two 16-bit words entirely.
  • DCBA (Little-Endian): Both bytes and words are swapped.

Correcting Byte Swaps in PLCs

When a PLC reads Modbus data and the values appear erratic or wildly out of scale, a byte or word swap is usually required. Most automation platforms offer native solutions:

  • Siemens (TIA Portal): Utilize the SWAP instruction for WORD and DWORD manipulation.
  • Allen-Bradley (Studio 5000): The SWPB (Swap Byte) instruction easily reorders the data.
  • Standard IEC 61131-3: Use bitwise shift operations (SHL, SHR) or rotate commands (ROL) to manually restructure the payload.

Driver Configurations and Troubleshooting

Before writing complex PLC logic, check your SCADA or OPC server configuration. Modern drivers in platforms like Ignition or Kepware allow you to select the exact byte/word order (e.g., “CDAB”) directly in the tag properties, handling the translation automatically. If you must troubleshoot manually, comparing the raw Hexadecimal values from the device manual against the PLC tag will quickly reveal the correct endianness format.