Device Configuration

Understanding EDS & XML Device Files: Configuring PLCs and Field Devices

Every time you add a drive, sensor, or I/O module to your PLC network, you need a device file. Learn what EDS, GSD, GSDML, and IODD files are, how to read them, and how they configure your fieldbus devices.

2026-03-08 · 17 min read

EDS
XML
GSD
GSDML
IODD
Device Configuration

🗂️ What Are Device Description Files?

When you add a VFD, I/O module, or smart sensor to your PLC network, the engineering software needs to know: What data does this device send? What parameters can be configured? What communication settings does it support?

Device description files answer all these questions. They're standardized text or XML files provided by the device manufacturer that describe the device's communication interface. Without them, your PLC doesn't know how to talk to the device.

📄 EDS Files: EtherNet/IP Device Description

EDS (Electronic Data Sheet) files describe devices on EtherNet/IP and DeviceNet networks. They're plain-text files with an INI-like structure:

EDS File Structure

$ EDS File for ACME VFD Model 500
$ Created: 2026-01-15
$ Vendor: ACME Drives Inc.
[File]
    DescText = "ACME VFD Model 500 AC Drive";
    CreateDate = 01-15-2026;
    CreateTime = 10:30:00;
    Revision = 1.2;
[Device]
    VendCode = 999;               $ Vendor ID assigned by ODVA
    VendName = "ACME Drives";
    ProdType = 2;                 $ Product type: AC Drive
    ProdTypeStr = "AC Drive";
    ProdCode = 500;
    ProdName = "VFD Model 500";
    Catalog = "VFD-500-EIP";
[Device Classification]
    Class1 = EtherNetIP;[Connection Manager]
    Connection1 =
        04040002,                 $ Trigger & transport
        44640405,                 $ Connection parameters
        ,Assem101,                $ Input assembly (from drive)
        ,Assem102,                $ Output assembly (to drive)
        ,Assem103;                $ Config assembly

Understanding Assemblies

Assemblies define the I/O data layout — what bytes the PLC exchanges with the device every scan:

[Assembly] Assem101 = $ Input Assembly: Drive → PLC "Input Data", $ Name , $ Path 16, $ Size in bytes 0x0004, $ Descriptor , $ Reserved 2, $ Number of members StatusWord, $ Member 1: Drive status (WORD) ActualSpeed; $ Member 2: Speed feedback (REAL)

Assem102 = $ Output Assembly: PLC → Drive "Output Data", , 8, $ Size in bytes 0x0001, , 2, ControlWord, $ Member 1: Drive command (WORD) SpeedReference; $ Member 2: Speed setpoint (REAL)

How to Read This in Your PLC Code

// The EDS file tells us: // Input assembly (101): 16 bytes // Bytes 0-1: StatusWord (WORD) // Bytes 4-7: ActualSpeed (REAL) // Output assembly (102): 8 bytes // Bytes 0-1: ControlWord (WORD) // Bytes 4-7: SpeedReference (REAL)

PROGRAM EDS_DataMapping VAR // These tags map to the assembly data // In Allen-Bradley: auto-created from EDS import // In CODESYS: manually mapped to EtherNet/IP adapter Drive_StatusWord : WORD; // Input, bytes 0-1 Drive_ActualSpeed : REAL; // Input, bytes 4-7 Drive_ControlWord : WORD; // Output, bytes 0-1 Drive_SpeedRef : REAL; // Output, bytes 4-7 END_VAR

EDS Parameters Section

EDS files also define configurable parameters (CIP attributes) accessible via explicit messaging:

[Params] Param1 = 0, $ Reserved ,, $ Link/size 0x0006, $ Descriptor (read/write) 0xC8, $ Data type: REAL 4, $ Data size "Motor Rated Current", $ Parameter name "A", $ Units "0.1", $ Minimum value "999.9", $ Maximum value "12.5", $ Default value ,,; $ Reserved

Param2 = 0,,, 0x0006, 0xC8, 4, "Acceleration Time", "s", "0.1", "600.0", "10.0", ,,;

📋 GSDML Files: PROFINET Device Description

GSDML (General Station Description Markup Language) files are XML-based descriptions for PROFINET devices. They're more detailed than EDS files:

PROFINET Device Profile 1.00 Device Profile for ACME Sensor ACME Temperature Transmitter TT-200 4-20mA Temperature Module

Upper Range Value Lower Range Value

Reading GSDML: What Matters for Programmers

🔗 IODD Files: IO-Link Smart Sensors

IODD (IO Device Description) files describe IO-Link sensors and actuators:

ACME Sensors ProxSwitch PS-100 Distance Measured distance in 0.1mm

Switching Point 1 1000 Hysteresis 50

🔧 Practical Workflow: Using Device Files

Step-by-Step Process

📥 Download the file — Get the EDS/GSDML/IODD from the manufacturer's website (usually in the product's support/downloads section)

📂 Install in your IDE:

- TIA Portal: Options → Manage GSD files → Install → Browse to GSDML - Studio 5000: Tools → EDS Hardware Installation Tool → Add - CODESYS: Tools → Device Repository → Install

🔗 Add to hardware config — The device now appears in the hardware catalog. Drag it into your project's network view.

📊 Map I/O — The IDE creates I/O tags based on the assembly/module definitions in the device file. These become the variables you use in code.

⚙️ Set parameters — Configure device-specific parameters (scaling, filtering, communication settings) defined in the device file.

// After importing EDS and adding device to hardware config: // The I/O tags are automatically created: // EtherNet/IP (from EDS assemblies) Drive1_Input.StatusWord // Mapped from Assembly 101 Drive1_Input.ActualSpeed // Mapped from Assembly 101 Drive1_Output.ControlWord // Mapped to Assembly 102 Drive1_Output.SpeedRef // Mapped to Assembly 102 // PROFINET (from GSDML submodules) TempSensor_1.Temperature // Mapped from Submodule 1, Float32 TempSensor_1.Status // Mapped from Submodule 1, UINT8

// IO-Link (from IODD process data) ProxSwitch_1.Distance // Mapped from ProcessDataIn, UINT16

⚠️ Common Issues and Solutions

Summary

Device files are the Rosetta Stone of industrial communication. They translate between the device manufacturer's hardware design and your PLC's software model. Understanding their structure saves hours of commissioning time and eliminates the guesswork in I/O mapping.