What Is an EnDat Encoder? A Practical Guide for CNC and Servo Drives

EnDat is an interface, not a brand

EnDat is not the name of an encoder manufacturer. It is a digital, bidirectional serial communication interface used between an encoder and a drive, PLC or CNC controller.

An encoder with EnDat interface can typically provide:

• Single-turn or multi-turn absolute position feedback

• Optional incremental information or high internal interpolation for fine resolution

• Parameter data and electronic nameplate information

• Diagnostic values such as signal quality, temperature, warnings and error flags

So when we say “EnDat encoder”, we are talking about an encoder whose electrical output uses the EnDat protocol, usually as an absolute encoder that can also deliver much more than just position information.

How does an EnDat encoder work?

The EnDat interface is based on synchronous serial communication. On the drive side there is a master circuit. This master generates a clock signal and sends commands to the encoder. The encoder responds by sending the requested data back over a serial data line, bit by bit, synchronised with the same clock.

A simplified sequence looks like this:

1. The drive sends a command to the encoder, for example:

   • “Send current position value”

   • “Send diagnostic status”

   • “Read parameter memory”

2. The encoder prepares the requested data. Depending on the command, this may include single-turn or multi-turn position, a second position channel for safety applications, internal temperature, signal quality indicators or user parameters.

3. The data is then transmitted serially back to the drive in a defined bit structure, synchronised with the clock.

Because position, configuration and diagnostic information are all transported over the same interface, there is usually no need for separate reference switches, analogue signal lines or additional parameter cables. The wiring becomes simpler and the system delivers richer feedback to the control unit.

EnDat versions: EnDat 2.1, EnDat 2.2 and EnDat 3

Over time, the EnDat interface has evolved into several versions. In practice, the ones you will most often encounter are EnDat 2.1, EnDat 2.2 and the newer EnDat 3.

EnDat 2.1

EnDat 2.1 is an earlier generation of the interface. In some encoder models, digital EnDat data is combined with additional analogue sin/cos incremental signals. This has two main advantages:

• Backward compatibility with older drives that expect incremental inputs

• Possibility to achieve higher interpolation and resolution in the drive electronics

In new designs, EnDat 2.2 is usually preferred, but in retrofit projects EnDat 2.1 still plays an important role.

EnDat 2.2

EnDat 2.2 is one of the most widely used feedback options in today’s servo systems and CNC machines. Its main characteristics include:

• Fully serial communication: position and additional data are transferred via a single digital interface

• High internal resolution and fast data transfer for precise position control at high speeds

• Extended functionality, such as:

  • Diagnostic values, warning and error codes

  • Electronic nameplate and encoder parameters

  • OEM/user memory space

  • Commutation and limit position information

There are also safety-oriented variants of EnDat 2.2. These provide two independent position channels and safety-related status information so that machine builders can implement systems which satisfy functional safety standards when combined with appropriate drives and controllers.

EnDat 3

EnDat 3 is the next generation of the interface, designed for even higher data rates and richer data content. Key goals include:

• Faster and more detailed access to additional sensor and status information in the encoder (for example vibration or extended health data)

• Tighter integration into functional safety architectures

• Better support for Industry 4.0 concepts and condition monitoring in connected factories

For new machine platforms with a long expected lifetime, EnDat 3 is becoming an increasingly interesting option.

Advantages of using EnDat encoders

For a supplier like Fenac and for our customers, EnDat encoders offer technical and practical benefits that go beyond basic position feedback. The most important advantages can be summarised as follows.

1. Rich information over a single interface

Conventional incremental encoders primarily provide counting signals. Extra hardware and additional interfaces are typically required to access diagnostics or parameter data. With EnDat, position values, parameters and diagnostic information are all available through the same digital interface. This:

• Shortens commissioning time

• Speeds up fault finding during service

• Provides more data to the control system, which can be used for advanced functions such as predictive maintenance

2. Less cabling, cleaner design

Because EnDat is a serial interface, only a small number of conductors are needed between encoder and drive. This leads to:

• Slimmer cable harnesses and simpler cable routing

• Easier integration in moving cable chains

• Smaller connector sizes and reduced material cost

In multi-axis systems, the reduction in cabling complexity can have a significant impact on overall machine layout and reliability.

3. High resolution and dynamic performance

EnDat encoders combine high internal resolution with fast data transmission. As a result, they offer:

• Precise position control at high speeds

• Smooth motion at low speeds

• Fine interpolation and high repeatability

This makes them especially attractive for CNC machining centres, robotics, printing, packaging and other applications where both dynamics and accuracy are critical.

4. Built for functional safety

In applications such as presses, lifting equipment and collaborative robots, safety requirements are strict and position feedback must meet certain standards. Safety-oriented EnDat encoders support:

• Two independent position channels

• Integrated error detection and consistency checks

• Use in safety-certified drive systems according to SIL/PL levels

For machine builders, this simplifies the design of safe motion systems and reduces the need for additional hardware.

5. Easier commissioning and encoder replacement

With EnDat, encoder data such as type, resolution and counting direction can be stored in an electronic nameplate inside the encoder. During commissioning the drive can read this data automatically. This:

• Reduces the risk of parameter entry errors

• Speeds up start-up of new machines

• Simplifies encoder replacement in the field

For production environments, faster and more reliable service means less downtime and higher productivity.

Typical applications of EnDat encoders

EnDat interface encoders are used wherever precise and reliable position feedback is required, for example:

• CNC machining centres, lathes and milling machines

• Servo motor axes and linear motors

• High-precision linear stages and positioning systems

• Industrial robots and pick-and-place units

• Printing, textile, packaging and labelling machines

• Lifting systems, presses and other safety-critical motion applications

Within a portfolio like that of Fenac, EnDat-compatible encoders can support both new machine designs and retrofit projects where existing feedback systems are upgraded.

What to consider when selecting an EnDat encoder

Deciding that you “want EnDat” is only the first step. The encoder should be selected together with the drive and the mechanical design. Key points to clarify include:

• Required positioning accuracy and resolution

• Need for single-turn or multi-turn feedback

• Which EnDat versions (2.1, 2.2, 3) are supported by the drive or controller

• Cable length, cable type, EMC environment and connector standards

• Safety requirements and the possible need for a functionally safe encoder variant

• Mechanical interface: solid or hollow shaft, flange type, IP protection class, temperature range and vibration levels

Once these parameters are defined, it becomes much easier to choose the correct EnDat encoder model and the appropriate cabling and connector solution.