Basic Course

KNX System arguments












































KNX Association

KNX BASIC COURSE





Table of Contents

1 KNX Association: A brief outline .................................................................................. 3
2 Activities of KNX Association – International standardization ...................................... 4
3 KNX - difference compared to conventional technology .............................................. 5
4 KNX System specification ............................................................................................ 6
4.1 KNX Media...........................................................................................................6
4.2 Areas of application for the various media ........................................................... 7
4.3 Types of configuration .......................................................................................... 7
4.4 KNX interworking .................................................................................................8

5 Success figures ...........................................................................................................9
6 The advantages of KNX ............................................................................................... 9
7 KNX: Application examples ........................................................................................ 10
8 Selling the benefits .................................................................................................... 12























































Home and Building Management Systems KNX Association
KNX System arguments Arguments_E1213b 2/12

KNX BASIC COURSE


1 KNX Association: A brief outline


















Figure 1: KNX – The history

KNX Association has been set up in 1990 with headquarters in Brussels (Belgium), then
still called “EIB Association”. The goal of the association was to promote intelligent homes
and buildings in general and the EIB system in particular, which was developed jointly by
some renowned manufacturers.

In 1999 this association merged with two other European associations. These are:

BCI (France) promoting the Batibus system;
European Home Systems Association (The Netherlands) promoting the EHS system.
As a result of this merger, the name was changed into “KNX Association”.

KNX Association has the following goals:
definition of a new truly open standard ‘KNX™’ for intelligent homes and buildings;
establishing the KNX Trademark as a token for quality and multi-vendor interworking;
establishing KNX as a European and worldwide standard.

As EIB is backward compatible to KNX, most devices can be labelled both with the KNX
as well as the EIB logo.






























Home and Building Management Systems KNX Association
KNX System arguments Arguments_E1213b 3/12

KNX BASIC COURSE

2 Activities of KNX Association – International standardization

KNX Association runs the below activities:
The further technical development and the promotion of the KNX standard together
with the KNX member companies;
The further development of the common design and commissioning tool software
called ETS™;
Sales and support of ETS via the KNX Online Shop (https://onlineshop.knx.org);
Granting the KNX trademark for KNX compatible products (product certification);
Promotion of KNX training measures through the certification of training centres and
by making available training documentation;
National and international standardisation activities;
Encouraging the setup of national groups;
Promotion of “scientific partnerships” with technical institutes or universities in order to
promote the KNX system amongst students and for research;
Technical support for manufacturers wanting to develop KNX compatible solutions;
Definition of testing and quality standards together with the KNX member companies;
Promotional activities (web site, fairs, brochures…)

KNX Association consisted of 9 members when it was founded: this number has
meanwhile increased to more than 300 (situation November 2013). The current
membership list is available at any time under www.knx.org.





























Figure 2: KNX in standardization

At the end of 2003, the KNX Standard was approved by CENELEC (European Committee
of Electrotechnical Standardisation) as the European Standard for Home and Building
Electronic Systems as part of the EN 50090 Series. The KNX Standard was also
approved by CEN (EN 13321-1 for media and protocol and EN 13321-2 for KNXnet/IP). At
the end of 2006, KNX was also approved as a world standard (ISO/IEC 14543-3-1 to 7).
Moreover, in May 2013, the KNX technology has been approved as a Chinese standard
(GB/T 20965). KNX is also approved in the USA as ANSI/ASHRAE 135.


Home and Building Management Systems KNX Association
KNX System arguments Arguments_E1213b 4/12

KNX BASIC COURSE

3 KNX - difference compared to conventional technology
































Figure 3: KNX – introduction to the technology
In the case of the most widely used medium “Twisted Pair”, a control cable is laid parallel
to the 230 V cable. This results in the following advantages compared to conventional
installation technology:
the amount of cabling is considerably reduced when bus devices are arranged in a
decentralized way;
Increase in the number of possible system functions;
Improvement of the transparency of the installation.

This control cable:

connects loads (actuators) and switches (sensors)
supplies power to the bus devices in most cases.

As all KNX bus devices have their own intelligence, a central control unit (e.g. PC) is not
necessary. KNX can therefore be used both in small installations (flats) as well as large
projects (hotels, administration buildings...).





















Home and Building Management Systems KNX Association
KNX System arguments Arguments_E1213b 5/12

KNX BASIC COURSE

4 KNX System specification


4.1 KNX Media



































Figure 4: KNX System overview

As explained in the previous paragraph, the exchange of KNX data between devices is
typically done via a separate control cable. KNX data can also be sent via the existing 230
V cable (“Powerline transmission medium”), wireless (“KNX Radio Frequency
transmission medium”) and via Ethernet/WIFI (“KNX IP”). Via appropriate gateways,
transmission of KNX telegrams is also possible on other media, e.g. optical fibre.

When connecting different media, appropriate media couplers have to be used. The used
medium of a device is visible on the product’s label.




























Home and Building Management Systems KNX Association
KNX System arguments Arguments_E1213b 6/12

KNX BASIC COURSE

4.2 Areas of application for the various media























Figure 5: Areas of Application for the various media

4.3 Types of configuration

Depending on what is marked on the label of the device, devices can be configured (i.e.
linked and setting of parameters) via:

Easy installation techniques (E-Mode): configuration is done without the help of a PC
but with a central controller, push buttons…
This type of configuration is intended for the skilled contractor with basic bus
knowledge. Easy compatible products normally have limited functionality and are
intended for medium size installations.

System installation techniques (S-Mode): design of the installation and configuration is
done via a PC with the installed manufacturer-independent ETS Software, whereby
the manufacturers’ product data are imported in ETS.
This type of configuration is intended for KNX certified building designers and
contractors and for large size installations.

Some devices allow configuration via easy installation techniques as well as S-mode . For
1
instance, products with the LTE label are normally configured via the LTE (Logical Tag
Extended) mechanisms: all devices however include a defined S-mode interface, which
allows linking them with S-mode compliant devices.
















1 In the case where the product is also labelled with the EIB logo and the KNX logo, this implies
that the product uses the medium TP and can be configured by ETS.

Home and Building Management Systems KNX Association
KNX System arguments Arguments_E1213b 7/12

KNX BASIC COURSE

4.4 KNX interworking



























Figure 6: KNX interworking
Devices from different manufacturers and functional areas that are labelled with the KNX
trademark and using the same configuration mechanism can be linked to form a
functioning installation thanks to the KNX standardization of
Telegrams: devices usually use standard telegrams for transmission, but in
exceptional cases they also use telegrams with extended length for the transmission
of bulky data ;
Useful data in telegrams: for various functions (amongst others switching, dimming,
shutter control, HVAC …), predetermined formats need to be used in KNX certified
devices.







































Home and Building Management Systems KNX Association
KNX System arguments Arguments_E1213b 8/12

KNX BASIC COURSE

5 Success figures
2
Millions of installed products
thousands of KNX registered and certified products
more than 300 KNX members (manufacturers)
more than 250 recognized training centres
10 international test labs
hundreds of thousands of implemented projects


6 The advantages of KNX

Increased safety
Economic use of energy during the operation of buildings
Simple adaptation of the electrical installation to the changing requirements of the user
Higher degree of convenience
future-proof installations
Wide range of available off-the-shelf components from many manufacturers
Large service network of qualified contractors/designers/integrators

The above arguments may be evaluated differently depending on the type of client or the
user of the installation e.g. functional building compared to residential building, able-
bodied people compared to disabled people, young people compared to elderly people,….











































3 For current figures, please consult the KNX web site (www.knx.org)

Home and Building Management Systems KNX Association
KNX System arguments Arguments_E1213b 9/12

KNX BASIC COURSE

7 KNX: Application examples




























Figure 7: Possible application fields


Example 1: Implementation of central functions – when you are leaving
the building, all lights, the water supply and specific sockets (electric
oven…) can be switched off, the KNX alarm system can be activated
and the blinds can be controlled dependent on the time of day, all with a
single command.



Example 2: In conference rooms, theatres as well as living rooms, it is
possible to activate different light scenes depending on the activity.
These light scenes can also be modified by the user at any time. For
example in administration buildings, it is possible to achieve an energy
saving of up to 75% for lighting by implementing constant light control
with only one brightness sensor on each building façade.


Example 3: All the states of the equipment in a flat can be indicated in
clear text and controlled via display units (fixed but also mobile devices
such as smartphones or tablet computers). In the same way This can
be implemented in larger installations using PCs and visualisation
software.













Home and Building Management Systems KNX Association
KNX System arguments Arguments_E1213b 10/12

KNX BASIC COURSE

Example 4: By interfacing a KNX installation with the telephone
network, the user can influence or query the building management
functions (e.g. the heating) using a mobile phone. Alarm signals can be
automatically routed to any required telephone number. KNX
installations can also be remotely serviced and configured by the
installer using any available media (e.g. the Internet). The time required
for maintaining the building management system is thus considerably
reduced.

Example 5: A large conference room should be divided into several
independent areas, if the need arises. By inserting partition walls, the
KNX installation automatically detects the required assignment of
switches and lights per room section. It is therefore not necessary to
change the existing cabling.

Example 6: Any number of panic switches (e.g. activation of all the
lights) can be installed.
At night, the lights between the children’s bedroom and the bathroom

can be activated by pressing a button and deactivated after a set
period.

Example 7: KNX enables individual room control of the heating and
cooling system with the creation of heating and cooling profiles per
room. The heat or cold input for a room is automatically adjusted when
a window is opened. In this way, an energy saving of more than 30%

per year can be achieved.
The heat generation can also be controlled dependent on the heat
requirement of the individual rooms (heat is only produced when it is
actually required).

Example 8: KNX enables presence simulation during the absence of
the building owner.





Example 9: The energy consumption of individual electric circuits can
be monitored by energy sensors /energy actuators and can be switched
off for load management when exceeding predefined threshold values.
Combined with a gateway to Smart Metering devices or renewable
energy sources, it is therefore possible to ensure the optimal use of

self-generated energy (e.g. in combination with a future electric
vehicle).













Home and Building Management Systems KNX Association
KNX System arguments Arguments_E1213b 11/12

KNX BASIC COURSE

8 Selling the benefits

































Figure 8: Selling the benefits


During a consultation with a future customer, the electrical contractor or designer should
discuss KNX only in terms of its benefits to the customer and focus on the customer’s
needs. Technology and costs should at first not be in the foreground. This discussion
should result in a system quotation rather than a component quotation. The process
should continue as follows:
Discuss the system quotation with the customer and again stress the benefits for the
customer;
If the price for the system is not acceptable, functions should be redesigned (e.g.
switching instead of dimming);
In extreme cases, the price of the installation can be reduced using the following
components:

 push button interfaces together with conventional push buttons
 push button BCUs
 multiple fold switch actuators






















Home and Building Management Systems KNX Association
KNX System arguments Arguments_E1213b 12/12

KNX System overview












































KNX Association

KNX BASIC COURSE





Table of contents

0 Definition...................................................................................................................... 3
1 Minimal structure of a KNX TP installation ................................................................... 4
2 Addressing................................................................................................................... 5

2.1 Individual address................................................................................................6
2.2 Group address .....................................................................................................7
2.3 Configuration steps............................................................................................11
2.4 Function after commissioning stage .................................................................. 12

3 Group object ..............................................................................................................13
4 Useful data of a TP telegram ..................................................................................... 14
5 Standardised datapoint types .................................................................................... 15

5.1 On/Off (1.001) ....................................................................................................16
5.2 Functional block „Shutter and blinds actuator - basic“ ....................................... 17
5.3 Functional block „Dimming“ ............................................................................... 18

5.3.1 Switching - On/Off (1.001) .............................................................................. 18
5.3.2 Relative dimming (3.007) ............................................................................... 18
5.3.3 Absolute dimming – Scaling (5.001) .............................................................. 19

5.4 2-octet float value (9.0xx) ................................................................................... 19

6 TP bit structure .......................................................................................................... 20
7 Telegram collision......................................................................................................21
8 Symmetrical signal transmission................................................................................ 22
9 Superimposing data and supply voltage .................................................................... 23
10 Connection of the power supply unit to the TP bus ................................................... 24
11 Cable lengths ............................................................................................................. 25

11.1 Cable length between TP power supply unit – TP bus device ........................... 26
11.2 Cable lengths between two TP bus devices ...................................................... 27
11.3 Total cable length per TP line segment ............................................................. 27

























Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 2/27

KNX BASIC COURSE

0 Definition


The following terms are used as synonyms in KNX literature:


Terms used in the KNX training
documentation and in ETS Alternative term

Individual address Physical address

Group object Communication object





































































Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 3/27

KNX BASIC COURSE


1 Minimal structure of a KNX TP installation





































Figure 1: Minimal structure of a KNX TP installation


A minimum TP KNX installation consists of the following components:

KNX Power supply unit (30 V DC)

Choke  Can also be integrated in the power supply
unit.

Sensor(s)  A single push button with two rockers is
represented in the figure above

 Sensors usually get their power from the
KNX power supply unit.

Actuator(s)  A single switch actuator is represented in
the figure above

Bus cable  only two wires of the bus cable are
required
 In the figure above it is represented as a
green line

 Connects sensors, actuators and KNX
power supply unit.

 Serves for data exchange and for providing
ancillary power


Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 4/27

KNX BASIC COURSE

2 Addressing

In KNX there are two types of addressing, i.e. the individual addressing and the group
addressing.








































Figure 2: Addressing







































Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 5/27

KNX BASIC COURSE

1
2.1 Individual address











Figure 3: Structure of the individual address


An individual address shall be unique within a KNX installation. Its primary goal is to
forward “programming telegrams”, new application - / and parameter data via the ETS to
the bus device.

The individual address in a telegram has a fixed structure of 16 bits and has the format as
shown in the figure above.
In the user interface of ETS and in KNX documentation, individual addresses are
represented in decimal format with two separating points.

The bus device is usually prepared for the acceptance of its individual address by
pressing a programming button on the bus device. The programming LED is lit during this
process.
The individual address is permanently assigned to the bus device by means of ETS. ETS
is now able to forward all required data (application, configuration, parameters, group
address assignments) via the bus to the device.

If the commissioning including all customization and diagnostic steps have been carried
out, the communication (e.g. light on/off) is exclusively done via group addresses.

































1 Synonym for “physical address”

Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 6/27

KNX BASIC COURSE

2.2 Group address

































Figure 4: Structure of group addresses

The normal communication between devices in an installation is carried out via group
addresses. The project engineer defines for each function in the installation an
appropriate group address. He can freely select the group address structure.

2
65535 group addresses are available . Only the group address 0/0/0 is reserved for so-
called broadcast communication (telegrams to all available bus devices). An example of a
broadcast message is the allocation of an individual address.






























2 Only valid from ETS4 onwards. Until ETS3 the most significant bit was set to 0. Main groups were
therefore limited from 0….15. 32767 group addresses were available in total.

Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 7/27

KNX BASIC COURSE

For each ETS project it is possible to select the representation of group addresses in a:
3-level structure (main group / middle group / subgroup)
2-level structure (main group / subgroup)
Freely defined structure

The levels only serve for a clearer overview of the functions / group addresses created in
ETS.

The default level is the 3-level structure. The level structure can be set for each project in
the project properties of ETS.

Example of a 3-level structure:

5/2/66 Room 424, switch light 1
5/2/67 Room 424, switch light 2
5/2/68 Room 424, switch all lights together
14/2/69 Switch lighting building 4
Etc.

The free group address structure offers the most flexible structuring option (see chapter
Project planning – Basic).

The meaning of each individual level can be freely defined by the ETS project engineer.
A common structure is however the following:

Main group Floor number

Middle group Functional domain (e.g. 1 = lighting, 2 = heating, 3 = Shading, …)

Subgroup Function of load or group of loads
(e.g. Light 1 R424 on/off, Window bedroom open/close, Ceiling living
room on/off, Ceiling living room dimming, Blinds room 424 up/down,…)



























Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 8/27

KNX BASIC COURSE










































Figure 5: Example: structure of group addresses in ETS


It is recommended to define a company default group address structure and to stick to this
structure in all projects in order to facilitate the insight into different projects.

Each group address can be assigned to bus devices at one’s discretion, regardless where
the device is installed.

The group addresses are assigned to the group objects of the respective bus devices,
either with the help of ETS (S-mode) or automatically and invisible in E-mode.



























Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 9/27

KNX BASIC COURSE

Summary:
The individual address is important for the commissioning and diagnostic in an installation
via ETS (in order to address individual devices).

Group addressing dominates however during “normal operation” of a KNX installation : in
that case, the individual address is of a lesser importance.

Address type Application See example letter post

Individual address Target address in ETS „programming To
telegrams“ in order to forward to one John Smith
single bus device new application – / Samplestreet 12
and parameter data. US-12345 Tinseltown

Group address Target address in „normal“ operation Bulk mail
telegrams like e.g. “Lighting room 424 To all households with a
on/off” photovoltaic installation


Important note :
3
Actuators can listen / react to several group addresses.

Sensors can however send only one group address per telegram

Note:
When using main groups 14 to 31 in ETS, one should take into account that these
group addresses could until now not be filtered individually by TP line -/ backbone
couplers. This could negatively influence the dynamics of the entire bus system.
Consequently, these main groups are to be used primarily for central functions.
The number of group addresses that can be assigned to sensors and actuators is
variable and is limited by the memory size of the bus device. ETS will prevent that the
available memory space is exceeded and will give an appropriate warning to the ETS
user.























3 These rules of thumb have been somewhat simplified. More precisely, one should state: group
objects can react to several group addresses, however - after an event (e.g. pressing a rocker) -
only the first group address assigned to a sensor object will be used during sending.

Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 10/27

KNX BASIC COURSE

2.3 Configuration steps

After mounting the devices, a KNX installation (especially for S-mode compatible
products) is not ready for operation until sensors and actuators have been loaded with the
application software via the ETS program. The project engineer first needs to carry out
the following configuration steps using ETS:


assigning individual addresses to the different devices (for the unique identification
of a sensor or actuator in a KNX installation);
selecting the appropriate application software for the bus devices;
Setting the parameters for the bus devices;
Assigning group addresses in order to logically connect sensors and actuators and
by doing so realize the desired functions.

In the case of E-mode compatible products, the same steps as above are applied,
whereby the settings for:

the individual addresses, but also
the parameters of the bus devices and
the group addresses (for linking the functions of sensors and actuators)

is done either via local settings on the products or automatically or semi-automatically by
a central controller module.
















































Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 11/27

KNX BASIC COURSE

2.4 Function after commissioning stage






































Figure 6: Function after commissioning stage

After configuration, the installation functions as follows:


If the upper rocker of the single push button (1.1.1) is pressed, it sends a telegram
containing the group address (5/2/66) and the value (“1” = switch on)
This telegram is received and evaluated by all connected bus devices.
All devices that have the same group address will:

 synchronously send an acknowledgement telegram (reception correct / reception
incorrect);
 read the value and behave accordingly.
In our example, the switch actuator (1.1.2) will close its output relay because group
address 5/2/66 was also assigned to it.
When the lower rocker is pressed, the same happens except that this time the value is set
to “0” and the output relay of the actuator is opened.















Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 12/27

KNX BASIC COURSE

3 Group object





Push button 2‐fold Switch Actuator 2‐fold


No. 0 5/2/66 Left rocker No. 0 5/2/66 Channel A

No. 1 5/2/67 Right rocker No. 1 5/2/67 Channel B

Individual address
1.1.1
Individual address

2 1.1.2



2








230 V
KNX

Figure 7: More detailed description of bus devices with group objects

In the previous introduction example, a group address was assigned directly to a bus
device (single Push button – single channel Actuator).

In reality, one needs to think one level deeper, as there can be several channels that can
communicate in a device. Obviously this is the case when a push button has more than
one rocker or when an actuator has more than one switching output.

The individual rockers of a push button or the several switching outputs of an actuator are
represented by so-called “group objects”.

KNX group objects represent memory locations in a bus device. The size of these objects
can vary between 1 bit and 14 bytes. The size of the group objects is defined by the
manufacturer and depends on the related function.

As only two states (0 and 1) are required for switching, 1 bit group objects are used in this
example. The data for text transmission is more bulky and therefore group objects with a
maximum size of 14 bytes are used.

ETS only allows linking by means of group addresses group objects with the same size.
Several group addresses can be assigned to one group object, but only one (the first one)
is the sending group address.



Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 13/27

KNX BASIC COURSE

Figure 7 shows the relation using a push button 2-fold and a switch actuator 2-fold as an
example.

A group communication in detail:
a) If e.g. the upper left rocker of a 2-fold push button is pressed, it will write a “1” to its
group object with the number 0. Consequently, the firmware in the device ensures that
a telegram is sent on the bus with the information “Group address 5/2/66, write value,
Value = “1”.
b) All bus devices mounted in the KNX installation, to which the group address 5/2/66
have been assigned (and thus listen to 5/2/66) will then take over the “1” in their own
group object. In our example, the actuator will take over the value “1” in its group
object with number 0.
c) The application software of the actuator establishes that the value in this group object
has changed and executes the switching process.



4 Useful data of a TP telegram

















Figure 8: Useful data of a TP telegram

The length of the data depends on the data point type used and can vary between 1 bit
and 14 bytes.






























Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 14/27

KNX BASIC COURSE

5 Standardised datapoint types


















































Figure 9: Standardised datapoint types (selection)
Several datapoint types were standardised to guarantee compatibility of similar devices
from different manufacturers (e.g. dimmer, clock).

Both the data format as well as structure of the group objects both for sensor and actuator
functions is part of the data point standardization.

The combination of several standardised datapoint types is called a functional block.

The name of a group object can be freely decided by the manufacturer. For instance, a
DPT_Step is sometimes, depending on the manufacturer, referred to as short operation or
as blind operation. This does however not imply that the use of the DPT is limited to this
area of application. For example “Scaling” (Type 5.001) can be used both for setting a
dimming brightness or for setting a heating valve position.

In the following pages examples of a number of data point types are presented. The full
list of all approved datapoint types can be downloaded from the KNX Association’s web
site (www.knx.org).



Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 15/27

KNX BASIC COURSE

5.1 On/Off (1.001)










































Figure 10: DPT On/Off (1.001),...

DPT_Switch (on/off) is used for switching an actuator function. Other one bit datapoint
types are defined for logical operations (Boolean 1.002), for Enable/Disable (1.003), etc....

Other functions or extensions to the pure switching function (inversion, time delay and
toggle switch functions etc.) are not part of the datapoint type, but are parameters of the
functional block specification, in which this DPT is used (e.g. functional block light switch).




























Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 16/27

KNX BASIC COURSE

5.2 Functional block „Shutter and blinds actuator - basic“


































Figure 11: Functional block “shutter and blinds actuator – basic”

The functional block “Shutter and blinds actuator –basic ” is especially used for controlling
shutter and blind drive mechanisms and consists of two group objects with the underneath
mentioned datapoint types:
Up/Down (DPT 1.008)
Step/Stop (DPT 1.007).


By writing on the object with ”Up/Down”, a drive is set in motion from an idle state or
changes direction while moving.

By writing on the object “Step”, a drive which is already in motion is brought to a stop or a
halted drive is set in motion (slats adjustment) for short periods (step-by-step).

Important: Group objects using this function should never reply to read requests via the
bus as they may unintentionally stop moving drives or set halted drives in motion. The
“read” flag should therefore be deleted in the relevant group objects – both in sensors as
well as actuators. This especially applies for central functions.

















Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 17/27

KNX BASIC COURSE

5.3 Functional block „Dimming“























Figure 12: Functional block Dimming


Apart from the 4 bit object (Relative dimming - DPT_Control_Dimming [3.007]), the
functional block dimming consists of at least a switching object (corresponds to
DPT_Switch [1.001]) and a value object (corresponds to DPT_Scaling – [5.001]).


5.3.1 Switching - On/Off (1.001)
Explained in § 5.1.


5.3.2 Relative dimming (3.007)

A dimming command, relative to the current brightness setting, is transmitted to the
dimming actuator using the relative dimming object DPT_Control_Dimming.

Bit 3 of the useful data determines whether the addressed device dims down or up
compared to the current brightness value.

th
Bits 0 to 2 determine the dimming step. The smallest possible dimming step is 1/64 of
100 % (1 % in the ETS group monitor).























Figure 13: Dimming steps in ETS

Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 18/27

KNX BASIC COURSE

5.3.3 Absolute dimming – Scaling (5.001)



















Figure 14: Scaling – Absolute dimming

With “Absolute dimming” (DPT_Scaling), a brightness value between 0,4 % (minimum)
and 100 % (maximum) is set directly.

Depending on the manufacturer‘s application, it may be possible to switch on
(0,4 % <= value <= 100 %) or off (value = 0) a connected device using this DPT.

This group object has a size of 1 byte.


5.4 2-octet float value (9.0xx)



















Figure 15: 2-octet float value (9.0xx)

With this data format positive or negative float values with a maximum resolution of 0,01
can be transmitted. This data format is used in many datapoint type definitions e.g. for
transmitting room temperatures in DPT „Temperature (°C)“ or „Speed (m/s)“.

Group objects with this data format have a size of 2 bytes.













Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 19/27

KNX BASIC COURSE

6 TP bit structure


































Figure 16: TP bit structure

A “bit” can have two logical states, i.e. “0” and “1”.

Technical logic in KNX TP:

During logical state “1” no signal voltage
During logical state “0”  signal voltage

This means that if several bus devices transmit simultaneously, the logical state “0” will
prevail!































Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 20/27

KNX BASIC COURSE

7 Telegram collision





















Figure 17: Telegram collision


A bus device with data to transmit may start transmission immediately if it detects that the
bus is unoccupied.

The simultaneous sending request of several bus devices is controlled by the CSMA/CA
procedure (Carrier Sense Multiple Access with Collision Avoidance).

The bus devices listen to the bus while transmitting. As soon as a bus device with the
logical state “1” detects the logical state “0” (= flow of current on the line), it stops
transmitting to give way to the other sending device.

The bus device that terminated its transmission continues to listen to the network to wait
for the end of the telegram transmission and then retries its transmission.

In this way, if several bus devices attempt to transmit simultaneously, the CSMA/CA
procedure ensures that only one of these bus devices can terminate its transmission
without interruption. The data throughput is therefore not reduced.































Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 21/27

KNX BASIC COURSE

8 Symmetrical signal transmission













































Figure 18: Symmetrical signal transmission

The data is transmitted symmetrically over the pair of wires. Not any of the wires is
connected to the ground or PE or has a fixed potential.

The bus device only evaluates the difference of the AC voltage between both wires.

As radiated noise affects both wires with the same polarity, it has no influence on the
difference in the signal voltage.























Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 22/27

KNX BASIC COURSE

9 Superimposing data and supply voltage































Figure 19: The transformer-IC in the bus device separates DC supply voltage and AC
Information voltage

Data is transmitted in the form of AC voltage. It is superimposed onto the DC supply
voltage. Both voltage parts are separated by the transformer-IC.















































Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 23/27

KNX BASIC COURSE

10 Connection of the power supply unit to the TP bus


































Figure 20: Connection of power supply to TP bus


The power supply feeds the bus via the choke. A voltage regulator is included in the
power supply, which tries to immediately correct deviations in the 30 V nominal voltage. If
the installation were connected directly to the power supply, the voltage regulator would
try to also correct the AC information voltage. This would result in a “tug of war” between
the sending bus device and the regulator included in the power supply.

The choke with its inductance brings some “inertia” into the system.
It allows short-time deviations to the 30 V voltage and at the same time allows the
regulation of the DC supply voltage.

The second task of the choke is the generation of the second (positive) half of the AC
voltage pulse. Only the first (negative) half is generated by the sending bus device. The
cooperation between bus device and choke results in an AC signal voltage without a DC
part. This is important for the correct signal evaluation in receivers.






















Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 24/27

KNX BASIC COURSE

11 Cable lengths






































Figure 21: cable lengths


Power Supply Unit - Bus device .................................................................... max. 350 m
Bus device - Bus device ................................................................................ max. 700 m
Total bus line length .................................................................................... max. 1000 m
Distance between 2 power supply units in one line………See manufacturer instruction

If using decentralised power supply, check the chapter ‘installation’.

































Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 25/27

KNX BASIC COURSE

11.1 Cable length between TP power supply unit – TP bus device



















































Figure 22: Cable length between TP power supply unit – TP bus device

A bus device only transmits a half wave (shown in the picture as the negative half wave at
the positive wire).

The choke as part of the power supply unit produces - together with the transformers of
the bus devices - the positive equalisation pulse.

As the choke plays a significant role in the forming of the equalisation pulse, the bus
devices may only be installed up to 350 m cable length away from the choke (power
supply unit).














Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 26/27

KNX BASIC COURSE

11.2 Cable lengths between two TP bus devices





































Figure 23: Cable lengths between two TP bus devices

A telegram transmission over the cable requires a certain transit time.
If several bus devices try to transmit simultaneously, a possible collision can only be
resolved up to a distance of 700 m (delay time of the signal tv = 10 µs).

11.3 Total cable length per TP line segment

The signal of the sending bus device will be damped by the continuous loading and
unloading of the cable capacity. At the same time, the signal edges are rounded by the
cable capacity. The signal level drops due to the resistive load (bus cable and device).

To ensure that data is reliably transmitted despite these two effects, the total cable length
per line segment may not exceed 1,000 m. The maximum number of devices per line
segment depends on their total power consumption.




















Home and Building Management Systems KNX Association
KNX System overview System overview_E1213a 27/27

KNX TP Topology













































KNX Association

KNX BASIC COURSE





Table of Contents

1 Topology - Overall view ............................................................................................... 3
2 Topology - Line and line segment ................................................................................ 4
3 Topology - Area ........................................................................................................... 5
4 Topology - Several areas ............................................................................................. 6
5 Individual address........................................................................................................7
6 Coupler - Gate function ................................................................................................ 8
7 Coupler - Block diagram .............................................................................................. 9
8 Coupler - Fields of application ................................................................................... 10
9 Connecting several lines............................................................................................11
10 Practical example for explanation of functionality ...................................................... 12
11 Internal line telegram ................................................................................................. 13
12 Line-crossing telegram............................................................................................... 14
13 Area-crossing telegram .............................................................................................. 15
14 Coupling unit: Routing counter................................................................................... 16
15 KNX - Internal and external interfaces ....................................................................... 17
16 Topology - Structure in building ................................................................................. 18
17 Backbone- /Line coupler classical structure ............................................................... 19
18 Taking into account higher telegram rates: IP Network ............................................. 20
19 Line couplers replaced by KNXnet/IP routers ............................................................ 22
20 Limits to the use of KNXnet/IP routers ....................................................................... 23
21 Informative annex - old line coupler type ................................................................... 24



In this chapter the following abbreviations are used:

BC = Backbone coupler
LC = Line coupler
DVC = Bus device
LR = Line repeater
PS/Ch = Power supply with choke
S = Brightness sensor
RC = Routing counter






















Home and Building Management Systems KNX Association
KNX TP Topology Topology_E1213a 2/24

KNX BASIC COURSE



1 Topology - Overall view



Backbone line
BC BC
x.0.0 DVC 1 DVC 49 15.0.0


Main line
LC
x.x.0 LC

DVC 1
Maximum x.x.1 DVC 1
64 devices
DVC 63 Secondary line (1st line segment)
x.x.63



LR LR LR
x.x.64 x.x.128 x.x.192 DVC 63

3 x DVC 65 DVC 129 DVC 193
maximum x.x.65 x.x.129 x.x.193
64 devices

DVC 127 DVC 191 DVC 255
x.x.127 x.x.191 x.x.255

Figure 1: Maximum topological size of a KNX TP installation
In the figure above the maximum topological size of a KNX TP installation is shown.

The overall view in the above figure shows the possibility to extend a KNX TP installation
by means of line extensions, resulting in different line segments.

A line can be extended once and this extension can be connected two times in parallel,
thereby using line repeaters.

This results into a maximum of 4 line segments.

A line extension is only possible in secondary lines!

In the below illustrations, the details of a KNX TP installation are described one by one.















Home and Building Management Systems KNX Association
KNX TP Topology Topology_E1213a 3/24

KNX BASIC COURSE

2 Topology - Line and line segment


DVC DVC 64



DVC 1 DVC



1st line segment

DVC

PS/Ch DVC


DVC DVC DVC

Figure 2: Topology - line and line segment

By means of telegrams, each bus device (DVC) can exchange information with any other
device.

Maximum 64 bus devices can be connected to a line segment.

Each line segment requires its own appropriate power supply .
1

The actual number of devices per line segment depends on the power supply selected
and the power required by the individual devices.




































1 This chapter assumes the use of central power supply units only. For distributed power supply
units, consult chapter “Installation”.

Home and Building Management Systems KNX Association
KNX TP Topology Topology_E1213a 4/24

KNX BASIC COURSE

3 Topology - Area


Main line = line 0
PS/Ch




LC 1 LC 15



PS/Ch PS/Ch

DVC 1 DVC 1








DVC 63 DVC 63

Line 1 Line 15
1st line segment 1st line segment

Figure 3: Topology - area

If more than 64 bus devices are to be connected in an installation, then in the default
topology (without line extensions) up to 15 lines can be connected to a main line via line
couplers (LC). This line structure is called an area.

It is also possible to have up to 64 bus devices on the main line. The maximum number of
bus devices on the main line decreases by the number of line couplers used.

On each secondary line (in the default topology, the first line segment) but also on each
main line a power supply unit is required.

Line repeaters may not be used on the backbone or in main lines.

In the default topology (without line repeaters) up to 1,000 devices can be installed in an
area.






















Home and Building Management Systems KNX Association
KNX TP Topology Topology_E1213a 5/24

KNX BASIC COURSE

4 Topology - Several areas

Area 15

BC 15
Hauptlinie Area 2
SV/Dr
BC 2
Hauptlinie Area 1
SV/Dr LK 1 LK 15
BC 1
PS/Ch
SV/Dr Main line SV/Dr
PS/Ch LK 1 LK 15
TLN 1 DVC 1
SV/Dr SV/Dr
LC 1 LC 15
TLN 1 DVC 1
PS/Ch PS/Ch
TLN 63 DVC 63
DVC 1 DVC 1
Linie 1 Line 15
1. Liniensegment 1st line segment
TLN 63 DVC 63

Linie 1 Line 15
1. Liniensegment 1st line segment
DVC 63 DVC 63

Line 1 Line 15
1st line segment 1st line segment

Figure 4: several areas

If more than 1,000 bus devices are to be connected in an installation or in order to have a
clear line structure in larger installations, the TP installation can be extended by mounting
backbone couplers (BC) via the backbone line.

It is also possible to mount bus devices in the backbone line (own power supply required).
The maximum number of bus devices in the backbone line decreases by the number of
backbone couplers used.

Within a maximum of 15 possible areas, in the default topology approximately 15,000 bus
devices can be connected to the bus system and in the extended topology (with line
repeaters) approximately 58,000.

By dividing the KNX TP installation into lines and areas, the functional reliability is
increased considerably.













Home and Building Management Systems KNX Association
KNX TP Topology Topology_E1213a 6/24

KNX BASIC COURSE

5 Individual address



PS/Ch
Backbone line
BC 1 DVC BC 15
1.0.0 0.0.>0 15.0.0


DVC
1.0.>0



PS/Ch Main line



LC 1 LC 15
1.1.0 1.15.0


PS/Ch PS/Ch

DVC 1
DVC 1 1.15.1
1.1.1
Line 1 1st line segment Line 15 1st line segment





DVC 63 DVC 63
AREA LINE 1.1.63 BUS DEVICE 1.15.63

A A A A L L L L B B B B B B B B

0...15 0...15 0...255

Figure 5: Individual address

The individual address serves to clearly identify the bus device and describes its location
within the topology.

A = 1…15 addresses the areas 1…15
A = 0 addresses the bus devices on the backbone line

L = 1…15 addresses the lines 1…15 in the areas defined by A
L = 0 addresses the main line of the respective area

B = 1…255 addresses the bus devices on the line defined by L
B = 0 addresses the coupler in the respective line

The individual address of an unloaded bus device is 15.15.255.
New bus devices are also delivered ex-factory with the individual address 15.15.255.






Home and Building Management Systems KNX Association
KNX TP Topology Topology_E1213a 7/24

KNX BASIC COURSE

6 Coupler - Gate function

Primary line











Line coupler or backbone coupler








Filter table

















Secondary line


Figure 6: Coupler: gate function

When setting the parameters, a filter table can be loaded into a (line -/ or backbone
coupler). The filter table is created automatically in ETS during the planning & design
stage and contains the active line-crossing group addresses.
All received group telegrams are routed by the couplers if they are listed in the filter table.

In this way, each line works independently. Only line-crossing telegrams are routed.

The yellow LEDs on the coupler flicker when a telegram is received on the respective line.

The line repeater passes on all telegrams; it has no filter table.


















Home and Building Management Systems KNX Association
KNX TP Topology Topology_E1213a 8/24

KNX BASIC COURSE

7 Coupler - Block diagram


New line coupler


Primary line on bus connector









Transformer




Flash‐ROM with RAM with
filter table and operating data Electrical
operating system
insulation 1000 V
LC/BC

2 1
Transformer
Secondary line Primary line






Secondary line on bus connector

Figure 7: Block Diagram: new line coupler type


The coupler is designed for DIN rail mounting. In operation, for current line couplers the
primary line as well as the secondary line is connected via standardised bus connectors.

Current couplers (as from July 2003 onwards) can be programmed both from the primary
line as well as the secondary line.

Current couplers are supplied from the primary line and only have one controller. This has
the advantage that the coupler can report secondary line power down.

Current couplers are equipped with Flash ROM memory. Contrary to the old coupler
types, they do not need backup battery power for supplying the memory containing the
filter table.

The couplers electrically isolate the lines from each other.










Home and Building Management Systems KNX Association
KNX TP Topology Topology_E1213a 9/24

KNX BASIC COURSE

8 Coupler - Fields of application































Figure 8: Coupler: fields of application

Backbone couplers, line couplers and line repeaters are identical devices. Their tasks
depend on the location and the corresponding assigned individual address.

The coupler can be used as:

Backbone coupler BC  Connection between: backbone line – main line
Line coupler LC  Connection between: main line – secondary line

Line repeater LR  For extending a line by a line segment with up to 64 additional
bus devices and an additional cable length of 1,000 m.

Backbone couplers and line couplers only forward line-crossing telegrams.
The line repeater does not have a filter table and therefore forwards all telegrams.

It is the assigned individual address that designates a coupler either as a backbone
coupler, a line coupler or a line repeater. The address 1.1.0, for example, defines the
device as the line coupler of line 1 in area 1.

The line coupler monitors the data communication between the main line and the
secondary line and vice versa. Only the telegrams of which the group addresses are
stored in its filter table are routed.












Home and Building Management Systems KNX Association
KNX TP Topology Topology_E1213a 10/24

KNX BASIC COURSE

9 Connecting several lines






Switch
PS/Ch
Actuator
Line 0












SV/Dr
Switch
PS/Ch LC
Actuator
2 1
Line 1












SV/Dr
Switch
PS/Ch LC
Actuator
2 1
Line 2

Figure 9: connecting several lines

In an installation consisting of several lines, each line or each line segment must have its
own power supply unit and choke.

The above figure shows a power supply unit with an integrated choke as well as the line
coupler.

Both lines, the secondary line (e.g. line 1) as well as the primary line (line 0) are
connected to line coupler (current version) via standard bus connectors.














Home and Building Management Systems KNX Association
KNX TP Topology Topology_E1213a 11/24