Technical Information

The EnDat 2.2 Bidirectional Interface for Position Encoders
Digital drive systems and feedback loops with position encoders for measured value acquisition require fast data transfer with hightransmission reliability from the encoders. Further data such as drive-specific parameters, compensation tables, etc. must also
be made available. For high system reliability, the encoders must be integrated in routines for error detection and have diagnostic
capabilities.
The EnDat interface from HEIDENHAIN is a digital, bidirectional interface for encoders. It is capable both of transmitting position values
from incremental and absolute encoders as well as transmitting or updating information stored in the encoder, or saving new information.
Thanks to the serial transmission method, only four signal lines are required. The data are transmitted in synchronism with the clock signal
from the subsequent electronics. The type of transmission (position values, parameters, diagnostics, etc.) is selected by mode commands
that the subsequent electronics send to the encoder. The EnDat 2.2 interface, a purely serial interface, is also suited for safety-related
applications with up to SIL 3.

Universal
High-performance
Communicative
Diagnostics-capable
Safe

EnDat 2.2: proven interface technology

Proven in daily operation
EnDat 2.2 is an established interface that enables flexible machine designs through a wide range of encoders together with its
intrinsic properties:
Universal• Broad selection of encoders fromvarious manufacturers• Convenient cabling– HMC 6 hybrid cable technology– M12 connection technology• Integration of additional sensors– Temperature sensors
High-performance• Short cycle times–1
 5 µs attainable with low positionmeasurement jitter• High transmission frequency andreliability–8 MHz at 100 m cable length or
16 MHz at 20 m

Diagnostics-capable• Electronic ID label for automatic systeminstallation– Data for encoder, motor, and system• Online encoder diagnostics– Together with the sensor data, forms
the basis for condition monitoring andpredictive maintenance• Storage of operating status data
– Storage via the subsequent electronics

Safe• For safety-related applications withup to SIL 3– Can be implemented with EnDat
Master Safe and EnDat Master Basic(according to the Black Channel
principle)

Communicative• Transmission of position values andsensor data–R
 olling output of additional data– Access to encoder memory duringclosed loop operation• Extensive system monitoring for
Industry 4.0– Automatic system installation anddiagnostics

Convenient connection technology,
8-wire cable, single shielding

Simple subsequent electronics
with EnDat 2.2 receiver chip
(EnDat master)Connecting
element, e.g.
M12, D-sub* For parallel power supply lines
Integrated interpolation and position value
formation, temperature measurement2

Supply voltage without
remote sense
UP = 3.6 V to 14 V

Thanks to the broad portfolio of EnDat 2.2
encoders, an optimal encoder is available
for any given application:• Encoders with different measuring andscanning methods– Absolute, incremental– Photoelectric, inductive, magnetic– Singleturn, multiturn with gears,
multiturn with buffer battery backup• Encoders with compatible mounting
solutions

Further information:
For our entire range of encoders, visit
www.heidenhain.de

AMO

RSF

NUMERIK JENALEINE LINDE

Strong brands for your applications:
AMO, ACU-RITE, ETEL, LEINE LINDE, LTN, NUMERIK JENA, RENCO, RSF

Automation• HMC 6 hybrid cable• Sensor integration (e.g., easy connectionof a temperature sensor in the servomotor)• Storage of operating status data
• System information for automaticconfiguration• Diagnostic capabilities• Functional safety
Machine tool
• Mechanically robust cabling• Integration of sensor boxes• System information for automaticconfiguration• Diagnostic capabilities• Functional safety
Electronics industry• System information for automaticconfiguration• Diagnostic capabilities–F– F utulex re– W ibl readid e m y teeraan chin chnolgeeof de ogy
en sigco ns
ders

The target industries for which EnDat
was designed stand to benefit inparticular from the following features:www.endat.de
The features of the EnDat interface and the wide range of available encoders permit theimplementation of machine design flexibility with future-ready technology.

3

The bidirectional interface

The EnDat interface is a digital, bidirectional
interface for encoders. It is capable ofoutputting position values, reading andupdating information stored in the encoder,and storing new information in the encoder.
Thanks to the interface’s serial transmission
method, only four signal lines are required.
The data are transmitted in synchronism
with the clock signal from the subsequent
electronics. The type of transmission(position values, parameters, diagnostics,etc.) is selected via mode commands sent
to the encoder by the subsequent
electronics. Some functions are available
only in conjunction with EnDat 2.2 mode
commands.
History and compatibility
The EnDat 2.1 interface, which has been
available since the mid-1990s, has since been
upgraded to EnDat 2.2 (recommended for
new applications). In terms of its communi­
cation, command sets, and time conditions,
EnDat 2.2 is compatible with EnDat 2.1
but also offers significant advantages. For
example, EnDat 2.2 permits the transfer of
additional data (sensor values, diagnostics,etc.) along with the position value without
initiating a separate request. This allows
the interface to support additional typesof encoders (e.g., encoders with buffer
battery backup, incremental encoders). Theinterface protocol has also been expanded,and the time conditions (clock frequency,
calculation time, recovery time) have been
optimized.
Supported encoder types
The following encoder types are currently
supported with the EnDat 2.2 interface(readable from the memory area of theencoder):• Incremental linear encoders• Absolute linear encoders• Incremental, singleturn rotational
encoders• Absolute, singleturn rotational encoders• Multiturn rotary encoders• Multiturn rotary encoders with buffer
battery backup
For the various encoder types, someparameters must be interpreted differently(see the EnDat specifications), or EnDat
additional data must be processed (e.g.,incremental encoders or encoders withbuffer battery backup).

4

Interface

EnDat serial bidirectional

Data transmitted

Position values, parameters, and additional data

Data input

Differential line receiver in compliance with EIA standard RS‑485
for the signals CLOCK, CLOCK, DATA, and DATA

Data output

Differential line driver in compliance with EIA standard RS‑485
for DATA and DATA signals

Position values

Ascending during movement in the direction of the arrow(see mating dimensions of the encoders)

Incremental signals

Depends on encoder» 1 VPP, TTL, HTL (see the respective incremental signals)

Ordering designations
The ordering designations define the core
specifications and provide the following
information:• Typical supply voltage range• Command set• Availability of incremental signals• Maximum clock frequency
The second position in the ordering
designation identifies the interface
generation. With encoders of the current
generation, the ordering designation canbe read from the encoder memory.
Incremental signals
Some encoders also provide incremental
signals. These signals are primarily used
for increasing the resolution of the position
value or for providing data to a second
subsequent electronics unit. Current
generations of encoders have a highinternal resolution and therefore no longer
need to provide incremental signals. The
ordering designation indicates whether an
encoder outputs incremental signals:• EnDat01 With 1 VPP incremental signals• EnDatH With HTL incremental signals• EnDatT With TTL incremental signals• EnDat21 Without incremental signals• EnDat02 With 1 VPP incremental signals• EnDat22 Without incremental signals
Note on EnDat01/02:
The signal period is stored in the encoder
memorySupply voltage
The typical supply voltage of the encoders
depends on the interface:
EnDat01
EnDat215 V ±0.25 V

EnDat02
EnDat22

3.6 V to 5.25 V or 14 V

EnDatH

10 V to 30 V

EnDatT

4.75 V to 30 V

Exceptions are documented in theSpecifications.
Command set
The command set describes the available
mode commands, which define theinformation exchange between theencoder and the subsequent electronics.
The EnDat 2.2 command set includes all
EnDat 2.1 mode commands. In addition,
EnDat 2.2 permits further mode commands
for the selection of additional data andenables memory accesses even in a closed
control loop. When a mode command fromthe EnDat 2.2 command set is sent to an
encoder that supports only the EnDat 2.1
command set, an error message is triggered.
The specific command set supported is
identified in the encoder’s memory area:• EnDat01/21/H/T	Command set 2.1
or 2.2• EnDat02/22		
Command set 2.2

EnDat01
EnDatT
EnDatH≤ 2 MHz (see without
propagation-delay
compensation in the diagram)

EnDat21≤ 2 MHz

EnDat02≤ 2 MHz or≤ 8 MHz or 16 MHz(see note)

EnDat22≤ 8 MHz or 16 MHz

In conjunction with long cable lengths,transmission frequencies of up to 16 MHz
place high technological demands onthe cable. For reasons concerning thetransmission technology, the adapter cableconnected directly to the encoder must not
be longer than 20 m. Greater cable lengths
can be realized with an adapter cable nolonger than 6 m and an extension cable.
As a rule, the entire transmission pathmust be designed for the respective clock
frequency.
Note on EnDat02
EnDat02 encoders may have a pluggable
cable assembly. In choosing the version of
the adapter cable, the customer decides
whether the encoder will be operated withor without incremental signals. This also
influences the maximum possible clock
frequency. For adapter cables with incre­
mental signals, the clock frequency islimited to 2 MHz; see also EnDat01. For
adapter cables without incremental signals,
the clock frequency can be up to 16 MHz.
The exact values are stored in the encoder
memory.

Cable length in m

Clock frequency
The clock frequency is variable between
100 kHz and 2 MHz depending on thecable length (maximum: 150 m). Withpropagation-delay compensation in thesubsequent electronics, clock frequenciesof up to 16 MHz or cable lengths of up to
100 m are possible. For EnDat encoders
with the ordering designation EnDatx2, themaximum clock frequency is stored in theencoder memory. For all other encoders,the maximum clock frequency is 2 MHz.
Propagation-delay compensation is intended
only for the ordering designations EnDat21
and EnDat22; for EnDat02, see the note
below.

Clock frequency in kHzEnDat 2.1; EnDat 2.2 without propagation-delay compensation
EnDat 2.2 with propagation-delay compensation (by the EnDat master)
Under certain conditions, cable lengths of up to 300 m are possible after consultation with
HEIDENHAIN

Position values
The position value can be transmitted withor without additional data. At the earliest,
the position value is transmitted to thesubsequent electronics after the calculation
time tcal has elapsed or after 14.5 clock
pulses. The calculation time is determined
for the encoder’s highest permitted clock
frequency, but for no more than 8 MHz.
For the position value, only the required
number of bits is transferred. The numberof bits thus depends on the respective
encoder and can be read from the encoder
for automatic parameterization.
Typical operating modes
Operating mode EnDat 2.1: This mode isfor encoders that provide additional
incremental signals. For generation of theposition value, the absolute position is readonce simultaneously with the incremental
position, and both are used in the calculationof the position value. The subsequent
generation of the position value in thecontrol loop is based on the incremental
signals. Only EnDat 2.1 mode commands
are used.
Operating mode EnDat 2.2: This mode isfor purely serial encoders. For position
value generation, the position value is readfrom the encoder during each control cycle.
EnDat 2.2 mode commands are typicallyused to read the position value. EnDat 2.1
mode commands are typically used to read
and write parameters after switch-on.
In a closed control loop, the EnDat 2.2
interface allows additional data to be queriedalong with the position, and it permits theexecution of functions (e.g., read/write
parameters, reset error messages, etc.).

Additional data
Depending on the type of transmission(selection via MRS code), one or two itemsof additional data can be appended to theposition value. The types of additional data
supported by the respective encoder are
saved in the encoder’s parameters.
Additional data encompasses the following:
Status information, addresses, and data
• WRN: warnings• RM: reference mark• Busy: parameter request
Additional data 1• Diagnostics• Position value 2• Memory parameters• MRS-code acknowledgment• Test values• Temperature• Additional sensors
Additional data 2• Commutation• Acceleration• Limit position signals• Asynchronous position value• Operating status error sources• Timestamp5

Parameters are stored in various memoryareas, e.g.:• Encoder-specific information• Information from the OEM (e.g.,
electronic ID label of the motor)• Operating parameters (datum shift,
instruction, etc.)• Operating status (alarms or warnings)
Monitoring and diagnostic functions of
the EnDat interface enable a detailed
inspection of the encoder. These include
the following:• Error messages• Warnings• Online diagnostics based on valuation
numbers for easily determining thefunction reserves of an encoder• Parameters for mounting the encoder

Absolute encoder

Subsequent electronics
Incremental
signals *)Absolute
position value

Operatingparameters

Operatingstatus» 1 VPP A*)
EnDat interface

Memory areas
The encoder provides multiple memoryareas for parameters. These memory areas
can be read by the subsequent electronics,
and some areas can be written to by theencoder manufacturer, the OEM, or theend user. The parameter data are stored inpermanent memory. This memory allows
only a limited number of write accesses
and is not designed for the cyclic storageof data. Certain storage areas can be writeprotected (resettable only by the encoder
manufacturer).

Parameters of the encoder
Parameters manufacturer forof the OEM
EnDat 2.1
EnDat 2.2

System information
EnDat provides for the availability ofsystem information about the encoder andthe system (i.e., electronic ID label):• Encoder parameters, which are all of theparameters needed for initial encoder
configuration, are stored in the encoder.
• System parameters can be stored in theencoder’s memory by the OEM or plantbuilder.
• System or process status data, referred
to as operating status data, can be
stored in the encoder during closed loop
operation.

» 1 VPP B*)*) D
 epends on thedeviceBasics of functional safety
EnDat 2.2 supports the use of encoders insafety-related applications. The standards
DIN EN ISO 13849-1 (successor to EN 954-1),
EN 61508, and EN 61800-5-2 are taken as
the basis for this. These standards describe
the assessment of safety-related systems
based on the failure probabilities ofintegrated components and subsystems,
for example. The modular approach helps
manufacturers of safety-related systems in
implementing their complete systems by
allowing them to build upon alreadyqualified subsystems.

Further information:
See “Functional Safety” at
www.endat.de

Input circuit of thesubsequent electronics

Data transmission

Encoder

Subsequent electronics

Dimensioning
IC1 = RS-485 differential line receiverand driver
Z0 = 120 

Incremental signals
Depends on theencoder (e.g., 1 VPP)

Further information:
FAQ: RS-485 Transceiver atwww.endat.de

6

1 VPP

Connection technology

Connecting elements
Encoders with EnDat 2.2 interface without
incremental signals use mainly 8-pin M12connecting elements, but also 9-pin M23.
M12 connector technology is in wide use
in industrial applications and has thefollowing advantages:• Cost-effective connection technology• Smaller dimensions• Simpler cable feed-through in machines• Thinner connecting cables (¬ 6 mm
instead of the previous 8 mm)• Higher reliability thanks to injectioncoated connection technology• Integrated lock mechanism as vibration
protection

CablesIn conjunction with long cable lengths,transmission frequencies of up to 16 MHz
place high technological demands on thecable. HEIDENHAIN cables are equal tothis task, not least because of a cable
design conceived specifically for thisapplication. We recommend using original
HEIDENHAIN cables.

Further information:

Voltage supply
The correct supply voltage and power
consumption are stated in each encoder’sspecifications. EnDat 2.2 encoders feature
an expanded supply voltage range from
3.6 V to 5.25 V or from 3.6 V to 14 V.
This makes it possible to design the voltage
supply of the subsequent electronics sothat the resulting voltage after attenuation
through cable length, cable cross-section,and current consumption can be processed
without correction (applies only for cable
assemblies from HEIDENHAIN). This meansthat monitoring the voltage at the encoderwith the encoder’s sensor lines and adjusting
the supply voltage through a controllable
power supply unit (remote sense) are nolonger necessary.

HMC 6Single-cable solution for servomotors
Servomotors normally require two
separate cables:• One cable for the motor encoderand• One power cable for the motor supply
With its Hybrid Motor Cable HMC 6,
HEIDENHAIN has integrated the encoderlines in the power cable. So now only one
cable is needed between the motor andelectrical cabinet.

Further information:

Brochure: Cables and Connectors

Product Information: HMC 6

Diagnostics
EnDat enables extensive encoder
monitoring and diagnostics without anadditional line. Its diagnostics generatevaluation numbers, error messages, andwarnings, and are a key ingredient inattaining high availability in the complete
system.

For analysis of encoder functionality,
valuation numbers can be read cyclicallyfrom the encoder. Valuation numbers
provide information about the current
status of the encoder and its function
reserve. The identical scaling for all
HEIDENHAIN encoders enables consistentanalysis. The function reserves, combinedwith other sensor data, serve as the basis
for condition monitoring and predictive
maintenance in the higher-level subsequent
electronics.

The important factors:• Machine utilization planning• On-site support for the service technician• Easy evaluation of the encoder’s function
reserve• Simplified troubleshooting for repairs• Generation of useful quality statistics

Further information:
Brochure: Interfaces of
HEIDENHAIN Encoders
Sample display of the function reserve

7

Overview of encoders

The comprehensive product program from
HEIDENHAIN offers solutions for applications
in which the highest possible accuracy,
reliable reproducibility and repeatability,
safe process management, high machine
dynamics, simple operation, and maximum
efficiency are required.
These products are therefore used mainlyin the following areas:• Machine tools• Electronics production• Automation facilities• Elevators• Medical technology

Rotary encoders

ExI 1300
seriesExI 1100seriesECN 1100/
EQN 1100seriesExN 1100/
ExN 1300
series

ECN 400/
EQN 400
seriesECI/EBI 4000 series

Angle encoders

The product program from HEIDENHAIN
also contains numerous encoders forsafety-related applications.
RCN 2000
seriesRotary encoders for servo drives,
machines, and larger systems
HEIDENHAIN offers suitable rotary encoders
for a wide variety of applications. The rotary
encoders for safety-related applications areavailable in different versions with absolute
position acquisition.

ECA 4000 series

RCN 5000
seriesRCN 8000 series

Angle encoders for rotary axes
Angle encoders are characterized by highaccuracy values in the arc second range
and better. The angle encoders for safetyrelated applications are available with andwithout integral bearing, and as sealed
encoders for mounting or as modular
encoders for integration.
Linear encoders for linear axes
HEIDENHAIN offers exposed and sealed
linear encoders for safety-related applications.
These linear encoders are available in various
sizes, lengths, and accuracy grades.

RCN 6000 series

Linear encoders
LC 400 series

LC 100 series

LIC 4000 series

Further information on implementation:          
 

The Implementation Guide provides an overview of which documents and their content
are intended for which readers, and the available implementation aids.
We would be happy to send you the following EnDat 2.2 specifications upon request:• EnDat 2.2 Interface Specification• EnDat 2.2 Hardware Specification• EnDat 2.2 Application Conditions for Functional Safety• EnDat 2.2 Application Notes
To see the Implementation Guide and submit a query, please visit www.endat.de383942-29 · 5 · 05/2021 · H · Printed in Germany