Technical Information

EnDat 3: Proven Interface Technology Continuously
Further Developed
EnDat is the ideal interface for digital drive systems and position control loops with position encoders for measurement feedback.
Transmission over its serial interface is both fast and dependable, and can also include additional data such as motor-specific parametersand sensor information. Its extensive diagnostics and the inclusion of encoders in troubleshooting routines ensure high system reliability.
These features and benefits have established EnDat as a standard and globally recognized interface for position encoders in the machine
tool, electronics, and automation industries. With a broad, multi-supplier portfolio of encoders featuring various measuring principles,machine and equipment manufacturers are sure to find the right EnDat encoder for their specific application and requirements.
EnDat 3 carries forward the features and benefits of EnDat into the future of digital manufacturing. To achieve this feat, EnDat 3 relies ona new architecture that not only preserves proven technology but also maintains the best possible continuity and compatibility withprevious versions.
What’s new with EnDat 3:• Hybrid cable transmission• Bus topologies• Sensors: flexible data contents and sensor box• Functional safety: black-channel communication• Higher data bandwidth• Definable send lists• System installation: introduction of access levels

3
UniversalHigh-performance
Communicative
Diagnostics-capable
Safe

EnDat 3: future-ready for digital manufacturing

Inception: EnDat 2.1
The EnDat story began in 1995 with theintroduction of EnDat 2.1. This first EnDat
version boasted the following features rightfrom the get-go:• Automatic system installation– Electronic ID label– OEM memory– Datum shifting• Alarms and warningsPurely serial: EnDat 2.2
The introduction of EnDat 2.2 in 2003 wasmarked by the transition to purely serial datatransmission and a strong focus on continuity
with the previous version. EnDat 2.2 also
added functionality in the following areas:• Functional safety• Temperature sensors• Online diagnostics (function reserve)• HMC 6 hybrid cable technology• Support of additional encoder types(e.g., with buffer battery backup)

1995

2003

2019

analog + serial

serialserialEnDat 3
EnDat 2.2
EnDat 2.1

Future-ready: EnDat 3
The arrival of EnDat 3 on the market marks a new interface generation that continues to develop and expand on the features ofthe EnDat family for the digital future of industrial manufacturing:
Universal• Wide range of encoders from variousmanufacturers• Convenient cabling– HMC 2 hybrid cable technology– Bus operation– Integration of sensor boxes• Integration of additional sensors– Sensors integrated into the encoder– External sensors
High-performance• Short cycle times–1
 5 µs attainable with low positionmeasurement jitter• High bandwidth–1
 2.5 Mbps at 100 m cable length or
25 Mbps at 40 m
Communicative• Transmission of position values andsensor data–S
 end lists permit predefinedcommunication for various operating
scenarios– Access to encoder memory during
normal operation• Extensive system monitoring for
Industry 4.0– Automatic system installation anddiagnostics– Sensor data

2

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– Data acquisition through the encoderSafe• For safety-related applications
up to SIL 3– Black-channel communication– Easy implementation thanks to data
separation for motion controller andsafety controller

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 mountingsolutions

AMORSF

The product portfolio for EnDat 3 is being
similarly developed.

The main industries for which EnDat
was originally designed, and for which
EnDat 3 is being further developed,
stand to benefit in particular from thefollowing features:Automation• HMC 2 hybrid cable• Bus operation• Sensor integration (e.g., easy connectionof a temperature sensor inside theservomotor, with characteristic curve
selection for a KTY 84-130 or PT 1000)• Acquisition and storage of operating
status data
• System information for automaticconfiguration• Diagnostic capabilities• Functional safety
Machine tool
• Mechanically robust cabling• Integration of complex sensors andsensor boxes• Multi-dimensional measurement
technology• System information for automaticconfiguration• Diagnostic capabilities• Functional safety

LEINE LINDE–F– M utu
a re– W chin readid e d y teerean sig chn
ge n fl olo
gof exen ibi yco lity
ders

NUMERIK JENA

www.endat.de
The features of the EnDat interface and the wide range of available encoders permit the implementationof machine design flexibility with future-ready technology.

Electronics industry• Weight reduction due to thinner cables
and bus operation• Multi-dimensional measurement
technology• System information for automaticconfiguration• Diagnostic capabilities

3

EnDat 3: overview of basic features

Interface
ProtocolRequest-response method in half-duplex mode

Physical layer

RS-485: 4-wire or 2-wire

Data rate

12.5 Mbps (25 Mbps)

Cable length

For 12.5 Mbps: max. 100 m / for 25 Mbps: max. 40 m

HPF send time (position availability in the master)

Typically 10 µs

Cycle time

Typically > 25 µs

Bus operation

Daisy chain

Functional safety

Designed for up to SIL 3, black-channel communication

Functions
Diagnostics

For condition monitoring and predictive maintenance

System information

Automated configuration and storage of operating status data

Access control

User authentication (e.g., for datum shift, OEM memory)

Ordering designations
The ordering designation defines key communication characteristics
Supported communication types

E30-R2

E30-R4

E30-RB

EnDat 3:
communication modulated onto power supply wires

––EnDat 3:–
communication + separate power supply wires (4 wires)

EnDat 3: bus operation––Sensor box integration–D
Encoder+Connection
designationHousing

4

Subsequent unit

DCc

Block diagram: 2-wire

UEL-Ubat
GNDL

RS-485

P_SD+C TRR

P_SD-RsRCm

Housing

EnDat 3: communication

EnDat 3 requires two wires for communication, and usually uses two additional wires
for encoder power. However, since the­digital data stream has no DC component,
communication can be modulated onto thesupply wires, thereby reducing the overall
number of wires to just two for certain­applications (e.g., hybrid motor cables).
The EnDat 3 interface specification follows
an OSI-based layer model.
The encoder side of the interface is referred
to as the slave, and the subsequent electronics side as the master. Communication
occurs in half-duplex mode. A communication cycle consists of a request from themaster followed by a response from theslave. The communication between masterand slave is subdivided into foregroundcommunication and background communication.

Foreground communication
Foreground communication is intended fordata that must be available in the communication cycle (e.g., controller cycle).
Requests and responses are structured inframes with a defined length. Each request
and response begins with a preamble (PRE)and ends with a postamble (POST). The REQ
request frame controls communication
with the encoder or triggers certain actions
within it (e.g. clearing of error messages)
and therefore also determines the contentsof the response. Regardless of the REQ
frame contents, the response frame ischronologically divided into high-priority
data and low-priority data.
A response contains the following
elements:• One HPF (High Priority Frame)
The HPF typically contains the encoder
position. Depending on the encoder,
other information can be specified fortransmission in the HPF as well.
• One LPH (Low Priority Header)
The LPH carries status information about
the subsequent data contents. It also
contains information about the send list
and the number of transmitted LPFs.
The send list specifies the chronologicalsequence of LPFs within the individual
communication cycles.
• Up to 15 optional LPFs (Low PriorityFrames)
LPFs can carry additional data, such as
diagnostic values, sensor information, orredundant information for functionalsafety.

47

Application
Layer

Angle

310

16 Bit MT

32 Bit ST

BGD

Foreground
Background (embedded in Foreground)
Send lists (pre-defined communication)
Bus operation....

Word 0ForegroundandBackground

Transport
Layer

Word 1
Word 2

Data Link /NetworkLayer

BUS REQ

Standardized position formats
Encoder profiles
Error handlingAccess levels....

Request Response procedure
Fixed data frames....

HPF LPH LPF LPF

RS-485, 2-wire / 4-wire
12.5 Mbps / 25 Mbps
Bus operation....

PhysicalLayer

EnDat 3 communication layer model

The LPFs used in EnDat 3 continue to buildon the concept of additional data found in
EnDat 2.2. The switch between various
LPFs is performed in accordance with a sendlist configured in the encoder’s memory.
Intervention in the controller cycle by thesubsequent electronics is not required.
The send list can be configured either inthe encoder’s volatile memory after eachrestart or permanently in its non-volatilememory. During operation, the send list
specifies which LPFs are to be included in
the response from cycle to cycle. Up toeight different send lists can be stored in
the memory. The type of request determines
which send list is active, thereby allowing
the subsequent electronics to react tovarious operating statuses with speed andflexibility.
A sample communication cycle is shown
below. A complete communication cycle
always contains the white fields, as well as
up to 15 optional LPFs (in gray). Each of theREQ, HPF, LPH, and LPF protocol contents
are safeguarded by a CRC (CyclicRedundancy Check).

Background communication
Some tasks, such as reading from andwriting to the encoder memory, have low
timing demands. For these kinds of tasks,
EnDat 3 defines a background channel.
Background communication is embeddedin the foreground communication and uses
its frames as transport carriers (REQ, LPH,LPF). The background channel thus makes
it possible to read from and write to theencoder memory in the controller cycle.
However, the background channel cannot
handle real-time demands.
Bus operation
Along with point-to-point operation, EnDat 3
also offers bus operation for special applications. In bus operation, a Bus Request
Frame is added in front of the Request
Frame, thus allowing multiple participants tosend responses in a single communication
cycle.

RequestPREREQ
4 ByteResponse
POSTPREHPF

LPH

LPF

8 Byte4 Byte8 BytePOST

Communication cycle

Further information:• EnDat 3 Interface Specification

5

EnDat 3: communication

Functional safety
EnDat supports the use of encoders
in safety-related applications. This capability
is based on the following standards:
DIN EN ISO 13849-1 (successor to EN 954-1),
as well as EN 61508 and EN 61800-5-2.
In these standards, safety-related systems
are assessed based on the failure
probabilities of integrated components
and subsystems, among other criteria.
This modular approach helps manufacturers
implement their complete systems byallowing them to build upon previously
qualified subsystems.
The functional safety provided with EnDat 3
encoders for applications up to SIL 3 isbased on the following factors:• Position value– Two independent position values: Pos1(high resolution) and Pos2 (low resolution,if applicable)– Comparison of Pos1 and Pos2 by thesafe control unit
• Forced dynamic sampling– Cyclic testing of the monitoring
function in the encoder• Error messages– Monitoring of error bits F1 and F2• Due to the black channel, a safe
EnDat Master is not required and isthus not part of the safety chain• Separation of communication to themotion controller and safe control unit
(e.g., separate error messages)

Diagnostics
EnDat enables extensive encoder monitoringand diagnostics without an additional wire.
Its diagnostics generate valuation numbers,
error messages, and warnings, and are a
key ingredient in attaining high availability inthe complete system.
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
For analysis of encoder functionality,valuation numbers can be read cyclicallyfrom the encoder. Valuation numbers provide
information about the current status of theencoder and its function reserve. Because
the scaling of valuation numbers is identicalfor all HEIDENHAIN encoders, consistentanalysis is possible. The function reserves,combined with other sensor data, serve as
the basis for condition monitoring andpredictive maintenance in the higher-level
subsequent electronics.

In short, this means the following:
Convenient implementation is possible
thanks to the black-channel approachcombined with standardized position data
formats and the option of relocating forced
dynamic sampling to the encoder.

Further information:• EnDat 3 Application Conditions for
Functional Safety

Sample display of the function reserve

6System information
EnDat makes system information available
about the encoder and the 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, and accessible areas can bepassword-protected.
• System or process status data, referred
to as operating status data, can be
stored in the encoder during normal
operation; the encoder can even acquire
operating status data on its own.
Access control
Memory areas can be protected by various
levels of user authentication. The available
access levels are OEM1, OEM2, and User.
Authentication is performed with a 32-bit
password. When the encoder is shipped, theOEM1, OEM2, and User areas are vacantand protectable by separate passwords.
Singleturn and multiturn information canalso be separately configured and protected.
Typical implementation:• OEM1 (motor manufacturer): singleturnis set, and OEM1 memory is written to.
A password is defined; the OEM1 area isprotected.
• OEM2 (machine manufacturer): multiturnis set, and OEM2 memory is written to.
A separate password is defined; theOEM2 area is protected.
• User (customer): the User memory canbe written to. A separate password isdefined; the User area is protected.

EnDat 3: connection technology

Encoders with the purely serial EnDatinterface predominantly use 8-pin M12 and9-pin M23 connecting elements. Thiswidespread connector technology offers
the following benefits:• Cost-effective connection technology• Smaller connector dimensions andthinner connecting cables

CablesHigh transmission frequencies over longcable lengths place rigorous technologicaldemands on the cable. Specificallydesigned for this purpose, HEIDENHAIN
cables are qualified to handle this type ofapplication. We therefore recommend
using HEIDENHAIN cables.

Through its lower number of wires, EnDat 3
offers further options for miniaturizing theconnection technology and adapting it to
the application requirements.

4-wire technology
In the 4-wire variant, the master powers
the encoder with one wire pair and uses a
second wire pair to communicate with theencoder.

Connection
designation
EncoderUEUp
0VSD+
SD-Housing

Subsequent unit

2-wire technology (HMC 2)
Unlike the 4-wire option, the 2-wire variant
requires additional hardware. In thisconfiguration, the subsequent electronics
both power the encoder and communicate
with it along a single wire pair. For thispurpose, the encoder power supply anddata stream are separated by frequency
dividing networks (one on the master andone on the slave).
4-wire bus in daisy-chain modeThis variant allows encoders to be operated
on a daisy-chain bus. Unlike the 4-wirevariant, the 4-wire daisy-chain bus variant
requires an additional transceiver branchinside the encoder. This additional transceiverbranch establishes the data connection tothe next encoder on the bus. The 4-wiredaisy-chain bus variant also supports the4-wire variant.
Sensor box
With the 4-wire variant, a sensor box canbe looped in.

GND
RS-485
RCm

Power supply
The supply voltage and power consumption
are stated in the specifications of eachencoder. For encoders with the EnDat 3interface, a supply voltage of 12 V (±5 %)is recommended.

R

Housing

4-wire block diagram

Further information:• EnDat 3 Hardware Specification• Brochure: Cables and Connectors• Product Information doc.: HMC 6• Product Information doc.: HMC 2HMC 2 single-cable solution:
standard components for a reliable connection

7

Product portfolio with the EnDat 3 interface

Rotary encoders and connection
technology for market introduction:• ECI/EQI 1100 inductive rotary encoders
for small motors• ECI/EQI 1300 inductive rotary encoders
for larger motors• The HMC 2 hybrid motor cable with an
M12 or M23 connector

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 3 specifications upon request:• EnDat 3 Interface Specification• EnDat 3 Hardware Specification• EnDat 3 Application Conditions for Functional Safety• EnDat 3 Master Instructions• EnDat 3 Application Notes
To see the Implementation Guide and submit a query, please visit www.endat.de1305415-20 · 0.5 · 11/2019 · H · Printed in Germany