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10 Practical example for explanation of functionality
































Figure 10: Practical example


The push button T1 shall switch the lights L11, L12 and L13.During configuration, group
address 5/2/66 is attributed to the push button. The same address is also attributed to the
actuators controlling the before-said lamps.

The push button T2 shall switch the lights L21, L22 and L23. During configuration the
group address 5/2/67 is assigned to it. Again the same address is attributed to the
actuators controlling these lamps.

The brightness sensor S1 shall also switch the lights next to the window (L11 and L21).
Group address 0/2/11 is therefore attributed to the sensor as well as to the actuators
controlling the window lights (L11 and L21).

The window lights can therefore be switched via the push button as well as the brightness
sensor.























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11 Internal line telegram

KNX


5/2/66 5/2/67
P1 5/2/66 L11 L21
0/2/11 0/2/11




P2 5/2/67 L12 5/2/66 L22 5/2/67






S1 0/2/11 L13 5/2/66 L23 5/2/67

Figure 11: Internal line telegram


Pressing push button P1 sends a telegram with the group address 5/2/66.

Although all bus devices listen in when the telegram is transmitted, only the actuators of
lamps L11, L12 and L13 with the same group address 5/2/66 execute the command.

If the brightness sensor sends the group address 0/2/11, all the bus devices on this line
listen in but only the actuators of the window lights L11 and L21 execute the command.












































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12 Line-crossing telegram

Main line




LC 1 LC 2


5/2/66 5/2/66
P1 L13
0/2/11
S1

5/2/67
5/2/67
P2 L21 0/2/11


5/2/66
L11 0/2/11 L22 5/2/67





L12 5/2/66 L23 5/2/67

Figure 12: Line-crossing telegram

If the brightness sensor is not connected in the same line as the lamp it has to control, it is
necessary to transmit its telegrams via the main line.

By its parameterization, the line coupler LC2 is aware of the fact that there are bus
devices outside its own “line 2” responding to telegrams transmitted by the brightness
sensor. LC 2 therefore routes the group telegram 0/2/11 onto the main line.

Line coupler LC1 is aware of bus devices on its “line 1” that respond to the group telegram
0/2/11 and therefore transmits the telegram into its line.

All the bus devices on this line listen to the telegram from the brightness sensor but only
the actuators controlling the lights L11 and L12 execute the command.


























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13 Area-crossing telegram

Backbone line

BC 1 BC 2





Main line


LC 1 LC 2
5/2/66 5/2/67
L11 L21
0/2/11 0/2/11
P1 5/2/66 S1 0/2/11


L12 5/2/66 L22 5/2/67




L13 5/2/66 L23 5/2/67

Figure 13: Area-crossing telegram


If brightness sensor S1 is mounted in another area, it can still address all bus devices via
the backbone line.

If the group address 0/2/11 is assigned to the brightness sensor, the telegram is routed to
line 1 via the backbone couplers BC 1 and BC 2 and line coupler LC 1.

The actuators controlling lights L11 and L21 in area 1, line 1 then execute the command.





































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14 Coupling unit: Routing counter


RC = 3




BC BC





RC = 4 RC = 2


LC LC



RC = 5 RC = 1






LR LR



RC = 6 RC = 0









DVC DVC

Figure 14: Routing counter

The telegram transmitted by the sending device contains a routing counter, of which the
initial count value is 6.

Each coupler decrements the routing counter and passes on the telegram as long as the
value has not reached 0.The filter table entries are taken into account.

If a service device, however, transmits a telegram containing a routing counter value of 7,
the coupling units do not alter this value. In this case the filter table is ignored and all line
couplers in the installation route the telegram. It finally reaches the bus devices it is
intended for, no matter which line they are connected to.

In case of (unintentional) loops in the installation, the routing counter limits the number of
circling telegrams.







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15 KNX - Internal and external interfaces



PS/Ch
Backbone line
BC 1 Gateway






PS/Ch Main line = Line 0 Other
systems


LC 1 LC 15



PS/Ch DVC 1 PS/Ch DVC 1


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






DVC 63 DVC 63

Figure 15: KNX - internal and external interfaces

KNX is open to be linked to any other system. The backbone line (or any other line) can
be connected via a gateway unit to e.g. PLC, ISDN, building management technology,
Internet etc.

The gateway unit converts the protocol bi-directionally.

Media couplers connect different types of KNX media (e.g. Twisted Pair and Power Line
110).

Parts of KNX installations can also be linked via optical fibre. The benefits of this are
electrical separation and greater cable lengths.





















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16 Topology - Structure in building






























Figure 16: Division of lines in a medium sized project (example)

After the above theoretical introduction, some practical information (the above picture is
by the way explained in detail in chapter “ETS Project Design – Advanced”).

Ideally, a building does not contain more than 50 installed bus devices per floor. Or one
can – as shown in the above picture, make a division according to the different wings of
the building. It is clear that in this case the better overview will be realised when line
numbers correspond to floor numbers and area numbers correspond to building - or wing
numbers.





































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17 Backbone- /Line coupler classical structure


Backbone‐/ Line coupler classic


Line 1.5 Line 2.5
LC LC
1.5.0 Floor 5 2.5.0



Line 1.4 LC Floor 4 LC Line 2.4
1.4.0 2.4.0


Main line 1.0 Main line 2.0
Line 1.3 LC Floor 3 LC Line 2.3
1.3.0 2.3.0



Line 1.2 LC LC Line 2.2
1.2.0 Floor 2 2.2.0



Line 1.1 LC LC Line 2.1
1.1.0 Floor 1 2.1.0
Area 1 Area 2
BC BC
(West wing) 1.0.0 Backbone line 0.0 2.0.0 (East wing)

Figure 17: Backbone- /Line coupler classical structure

Of course it will not be possible to realize this under all circumstances. As line repeaters
can be installed (as already indicated before), such a floor may be equipped with up to
253 devices, without having to violate the above structure (taking into account that line
repeaters have to be counted double as discussed before, the normal maximum number
of devices of 256 is reduced by 3). With that many devices it is possible to realize nearly
any application, thanks to the current evolution in the development of KNX devices and
the availability of input - / output devices with in the mean while more than 16 channels.




























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18 Taking into account higher telegram rates: IP Network






LAN

Router




Network ‐ Switch





KNXnet/ KNXnet/ KNXnet/
IP‐Router IP‐Router IP‐Router
1.1.0 1.2.0 1.3.0



PS/Ch PS/Ch PS/Ch


KNX KNX KNX
DVC
DVC
DVC
1.1.1 1.2.1 1.3.1
DVC DVC DVC
1.1.2 1.2.2 1.3.2

Figure 18: Replacing line couplers by so-called KNXnet/IP routers

As explained in the previous paragraph, gateways to other systems can be installed on all
levels. Increasingly, this is requested in bigger projects as a result of higher customer
demands.

An important reason is the increased telegram load, which can occur when the user
makes use of visualisation software and devices with a higher number of channels, all of
which automatically returning multiple status acknowledgements.. In the latter case, a
pure TP topology is overloaded as transmission speed on main – and backbone lines is
limited to 9,6 Kbit / sec. In such a case one can easily use an IP network as a substitute
for main – or backbone lines, by using the coupler type that was designed for this
purpose.

As you can see from the above picture, the main line has been replaced by an IP network.
This has the advantage that all vertical operations e.g. the (bi-directional) communication
between a building central and KNX is only determined by the bit rate of the secondary
line (Ethernet is at least 1000 times faster; with the so-called “Gigabit” – switches it is
possible to transmit data on the Ethernet 100 000 times faster). The parallel connection of
several lines is no longer an issue. The standardized type of communication applied here
is called “Tunnelling”. It is in other words the well-known gateway function, which is also
used by ETS for remote programming across IP. A building central can be connected
simultaneously to several gateways, multiplying the total data rate.

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A different story is the direct communication between the individual KNX lines. The
KNXnet/IP router makes use of another procedure which is called “routing”, or the actual
line coupler function. Principally it works in the same way as routing across a TP main
line: A KNXnet/IP router wanting to send a line-crossing telegram, will send this with a so-
called “Multicast” IP address into Ethernet. All other KNXnet/IP routers are assigned to
this multicast address, and are able to receive and evaluate this telegram. The normal line
coupler function is now again applied, i.e. the comparison with the also here required filter
table (group telegrams) or the line address (individual addressed telegrams) resulting in
the blocking or routing of telegrams, depending on the case.
Please note the following with regard to multicast addresses:
a) There is a dedicated worldwide registered KNX multicast address, which is pre-
programmed in the software of the KNXnet/IP router. This multicast address can
be changed within the limits of the available address range for IP communication.
b) The network switch and area router in the LAN network must be fit to handle
multicast telegrams. In case of doubt you should discuss this matter in advance
with your network administrator.
c) The multicast addresses cannot be used across Internet, except across a VPN
connection.























































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19 Line couplers replaced by KNXnet/IP routers


Line coupler replaced by KNXnet/IP Router


Line 1.5 KNXnet/ KNXnet/ Line 2.5
IP‐Router Floor 5 IP‐Router
1.5.0 2.5.0


KNXnet/ KNXnet/
Line 1.4 Floor 4 Line 2.4
IP‐Router IP‐Router
1.4.0 2.4.0

KNXnet/ KNXnet/
Line 1.3 IP‐Router Floor 3 IP‐Router Line 2.3
1.3.0 2.3.0


Line 1.2 KNXnet/ KNXnet/ Line 2.2
IP‐Router Floor 2 IP‐Router
1.2.0 2.2.0


KNXnet/ KNXnet/
Line 1.1 Line 2.1
IP‐Router Floor 1 IP‐Router
1.1.0 2.1.0
Area 1 Area 2
(West wing) Network (East wing)
(LAN)
Figure 19: Our picture again: line couplers have now been replaced by KNXnet/IP routers.
This picture represents the underneath explained case 1.

Just like the TP/TP coupler, the KNXnet/IP router can be used as a line coupler as well as
a backbone coupler. If the KNXnet/IP router replaces the line coupler, all main lines and
basically also the backbone line are replaced by Ethernet (Case 1).
If backbone couplers are replaced by KNXnet/IP routers, the normal line couplers can
remain, as only the backbone line is replaced by the LAN (Case 2).
Which case is more appropriate depends more or less on the - to be expected telegram
rate requirements on main – and backbone lines. Theoretically, a third case is possible, as
a combination of case 1 and 2, with normal TP areas with a KNXnet/IP router on top and
also with lines with IP routers instead of line couplers. This option should however be
chosen in exceptional cases. The topic is described in more detail in the KNX advanced
course.




















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20 Limits to the use of KNXnet/IP routers

Even if the high bit rate of Ethernet considerably facilitates heavy telegram traffic and
minimizes telegram loss, one should warn not to thoughtlessly program bus devices
sending out telegrams too frequently. The fast Ethernet will not help if for instance
telegrams are sent out simultaneously from all lines into one single line. To explain it with
a metaphor: the case would be similar to all cars accessing a 1,000 lane motorway via
100 entries but all of them also wanting to exit via a single lane exit. This is by the way not
a KNX related problem: it is common to all mesh structured data networks.
Only a meaningful organisation of communication between bus devices and lines will be
able to prevent a very unlikely but still possible loss of data.
This however should be easily possible if one has sufficient knowledge on bus devices
and their respective parameters.


































































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21 Informative annex - old line coupler type


Old line coupler type


Secondary line on data rail



Secondary line

Electrical insulation 600 V Spring contacts
Bus coupling
230 V
Logic Filter table 50/60 Hz > 100 ms buffer
SV +
Bus +
Lithium battery Bus ‐
> 10 years SV ‐
Bus coupling Power supply unit Choke Connector LC

640 mA
Main line


Primary line on bus connector

Figure 20: Block Diagram: old line coupler type

In earlier installations (until June 2003) line couplers were installed where power supply
for both bus couplers, logic and the filter table memory were supplied from the secondary
line.

The primary line of this type of coupler, which is 4 respectively 1 unit wide, is connected
via standardized bus connectors and the secondary line by means of a data rail (spring
contacts). The connection to the bus cable is established by means of a data rail
connector (2-pole or 4-pole).

A lithium battery (with a life span of more than 10 years) provides the backup supply for
the memory containing the filter table, also in the case of a bus power down. New line
couplers are equipped with a flash ROM memory and therefore do not need backup
battery power.






















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Table of Contents

1 TP Telegram: general .................................................................................................. 3
2 TP Telegram structure ................................................................................................. 3
3 TP Telegram: time requirement ................................................................................... 4
4 TP Telegram acknowledgement .................................................................................. 5
5 Chapter telegram: “Informative annex” ........................................................................ 6

5.1 Numbering systems .............................................................................................6

5.1.1 Decimal system ................................................................................................ 6
5.1.2 Binary system ................................................................................................... 6
5.1.3 Hexadecimal system ........................................................................................ 6

6 TP Telegram: control field ............................................................................................ 8
7 TP Telegram: source address ..................................................................................... 9
8 TP Telegram: target address ..................................................................................... 10
9 TP Telegram: check byte ........................................................................................... 11





















































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1 TP Telegram: general













Figure 1: TP telegram: general

When an event occurs (e.g. when a pushbutton is pressed), the bus device sends a
telegram to the bus. The transmission starts after the bus has remained unoccupied for at
least the time period t1.

Once the transmission of the telegram is complete, the bus devices use the time t2 to
check whether the telegram has been received correctly.

All “addressed” bus devices acknowledge the receipt of the telegram simultaneously.



2 TP Telegram structure














Figure 2: TP telegram: structure


The telegram consists of bus-specific data and the actual useful data, which provides
information about the event (e.g. pressing a push button).
The entire information is transmitted in the form of 8-bit long characters.

Test data for the detection of transmission errors is also included in the telegram: this
guarantees an extremely high level of transmission reliability.



















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3 TP Telegram: time requirement
























Figure 3: TP telegram: time requirement

The telegram is transmitted at a bit speed of 9600 bit/sec, i.e. one bit occupies the bus for
1/9600 sec or 104 µs.

A character consists of 11 bits. Together with the pause of 2 bits in between characters,
this adds up to a transmission time of 1.35 ms (13 bits) per character.

Depending on the length of the payload, the telegram consist of 8 to 23 characters, the
acknowledgement is only one character. Taking into account the bus free time of t1 (50
bits) and a time of t2 (15 bits) until the acknowledgment, a message will occupy the bus
between 20 and 40 ms.

A switching telegram (including acknowledgement) occupies the bus for 20 ms.
Telegrams for text transmission occupy the bus for up to 40 ms.



Example:

(8x13 bits) + (1x13 bits) + (t1 50 bits) + (t2 15 bits) + (Ack 11 bits) = 193 bits
193 bit x 0,104 ms = 20,07 ms



















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4 TP Telegram acknowledgement
























Figure 4: Telegram acknowledgement

The receiving bus device checks on the basis of the check byte contained in the telegram
the correct reception of information and acknowledges accordingly.

If a negative acknowledgement (NACK [transmission error detected] or BUSY [device
unable to process new information]) is received to a telegram sent on the bus, the sender
will repeat the telegram. The number of repeated telegrams is typically limited to three
times. This is also the case when an acknowledgement is missing.











































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5 Chapter telegram: “Informative annex”













Figure 5: Numbering systems


5.1 Numbering systems

The terms ‘base’ and ‘digit’ are used in the classification of numbering systems.
In every numbering system, the largest digit is smaller than the base by 1.

5.1.1 Decimal system

This is the most common numbering system. People think in terms of decimal numbers. If
no details are given about the numbering system, the decimal system is assumed.

5.1.2 Binary system

This numerical representation is very important in computing as a storage location in
memory can only assume two states (0, 1). The content of such a storage location in
memory is called a bit.

5.1.3 Hexadecimal system

A combination of 4 bits of the binary system produces a hexadecimal number. This results
in a clearer representation of data.
























Figure 6: Data formats









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Data formats
Different data formats are necessary for processing data. The contents of the data formats
can be presented in binary, decimal or hexadecimal form.

Number conversions
In order to be able to switch between the different numbering systems, values must be
converted.

Converting a binary or hexadecimal number into a decimal number
The number is split up into its individual powers, which are then added up.
0
1
2
e.g.: 0A9HEX = 0 x 16 + 10 x 16 + 9 x 16
= 0 x 16 x 16 + 10 x 16 + 9 x 1
= 169DEC

Converting a decimal number into a binary or hexadecimal number
The number is constantly divided by the base of the target numbering system (binary or
hexadecimal) until the original number equals zero. The remainder of each division form
the digits of the converted number, when read from back to front.
e.g.: Division Remainder
169 : 2 = 84 1
84 : 2 = 42 0
42 : 2 = 21 0
21 : 2 = 10 1 Reading order
10 : 2 = 5 0
5 : 2 = 2 1
2 : 2 = 1 0
1 : 2 = 0 1
169DEC = 1010 1001BIN

Converting binary numbers into hexadecimal numbers
Often binary numbers can be converted more quickly if they are split into tetrads. Each
tetrad then corresponds to a number in the hexadecimal system. Leading zeros may be
added.
e.g.: 0000 1010 1001 BIN
0 A 9 HEX






















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6 TP Telegram: control field


























Figure 7: TP Telegram: control field

If one of the addressed bus devices has returned a negative acknowledgement and the
telegram transmission is repeated, the repeat bit is set to 0.
In this way, it is ensured that bus devices that have already executed the appropriate
command will not execute the command again.

The transmission priority is only observed if several bus devices attempt to transmit
simultaneously.

The required priority (apart from system priority) can be set for every group object using
the ETS. The standard setting is low operational priority.







































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7 TP Telegram: source address





























Figure 8: TP Telegram: source address

In the above example 3.10.20 represents the individual address of the bus device 20 in
line 10 in area 3.













































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8 TP Telegram: target address































Figure 9: TP Telegram: target address


The target address is normally a group address.

The target address can also be an individual address (system telegrams). On the basis of
bit 17 the receiver can determine whether the target address is a group or individual
address:

If the 17th = 0, the target address is an individual address. Only one bus device is
addressed.

If the 17th bit = 1, the target address is a group address. All bus devices with this address
are addressed.






























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9 TP Telegram: check byte



































Figure 10: TP Telegram: check byte

In order to detect errors in telegram transmission, test data is transmitted in the form of
parity bits (character check) and check bytes (telegram check).

Each character of the telegram is checked for even parity i.e. the parity bit P gets the
value 0 or 1 to make the sum of all the bits (D0-D7 plus Pz) equal to 0.

In addition all characters of the telegram are checked for odd parity for each bit position,
i.e. the check bit S7 gets the value 0 or 1 to make the sum of all data bits D7 equals 1.

The combination of character check and telegram check is called cross check.





























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Table of Contents

1 Introduction .................................................................................................................. 3
2 Internal structure of a Bus Coupling Unit ..................................................................... 5
3 Type definition of an application module ..................................................................... 8
4 Overview of the most important KNX standardised system profiles ............................ 9

4.1 System profiles ....................................................................................................9
4.2 Detailed description of the above features ......................................................... 10
4.2.1 Access control ................................................................................................ 10
4.2.2 Serial number ................................................................................................. 10
4.2.3 Interface objects ............................................................................................. 10
4.2.4 Memory size ................................................................................................... 10

5 Classical application functions ................................................................................... 11

5.1 Dimming with start/stop telegram ....................................................................... 11
5.2 Dimming with cyclical telegrams ........................................................................ 12
5.3 Application function: 'dimming actuator' ............................................................. 13
5.4 Application function: drive control sensor .......................................................... 14
5.5 Application function: drive control ...................................................................... 15

6 Drive control object structure ..................................................................................... 16






In this chapter the following abbreviations are used:

PEI = Physical External Interface
BCU = Bus coupling unit
AM = Application module
TRC = Transceiver
SR = Shift register
DAC = Digital-Analogue Converter
















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1 Introduction


KNX



Bus device














BCU
AM

AM









PEI

Figure 1: Bus device

A functioning bus device (e.g. dimming/shutter actuator, multi-functional push button, fire
detection sensor…) principally consists of three interconnecting parts:

bus coupling unit (BCU)
application module (AM)
application program (AP)

Bus coupling units and application modules are offered on the market either separated or
built into one housing. They must however always be sourced from the same
manufacturer. When separated, the application module can be connected to the BCU via
a standardised or a manufacturer-specific Physical External Interface (PEI). This PEI
serves as

an interface to exchange messages between both parts
the power supply of the application module

Whether the application module and bus coupling unit fit together – also whether they can
be connected mechanically – has to be checked with the respective manufacturer. In case
of TP devices, the connection to the bus is mostly ensured via the standardised bus
connector (dark grey/red). In case of DIN rail devices, connection to the bus is sometimes
also ensured via contact blocks to a so-called data rail (see chapter “Installation”).






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When the BCU is an integrated part of the bus device, it is takes either the shape of a BIM
(Bus Interface Module) or a chip set. A BIM is a bus coupling unit without programming
button and LED (these are added to the application module). A chip set consists of the
1
core of a BIM, i.e. the controller and the transceiver .

BCUs are currently available for connection to three different media: Twisted Pair (Safety
Extra Low Voltage), Powerline 110 (mains power) and RF (KNX-RF). The classical bus
coupling unit contains apart from the physical coupling function (sending and receiving
bus telegrams), also the application program memory. Newer developments are however
also available that only assume the task of sending and receiving bus telegrams. The
“intelligence” or the operating system and application program are in this case an
integrated part of the application module.

Each bus device has its own intelligence thanks to the integrated operating system and
program memory in the BCU or in the application module: This is the reason why KNX is a
decentralised system and does not need a central supervising unit (e.g. a computer).
Central functions (e.g. supervision) can however if needed be realized via visualisation
and control software installed on PCs.


Depending on their main function, bus devices can basically be divided into three classes:
sensors, actuators and controllers. It is rare to have devices with pure sensor or actuator
functionality nowadays. E.g. each push button with LED status display also has an
“actuator” function and each actuator with status information has a “sensor” function.

In the case of a sensor, the application module transfers information about its actual
inputs (digital / analog) to the BCU. The latter codes this data and sends it on the bus.
The BCU therefore regularly checks the state of the inputs of the application module.

In the case of an actuator, the BCU receives telegrams from the bus, decodes them
and passes this information on to the application module, which then controls the
actual available outputs (digital / analog).

A controller regulates the interaction between sensors and actuators (e.g. logical
module) and has no physical inputs and outputs.

In the case of S-mode compatible KNX devices, a device receives its predetermined
function once the appropriate application program for the application module has been
loaded into the program memory (via the ETS). An S-mode compatible KNX push button
mounted on a BCU can only generate dimming signals, after the suitable application
program has been programmed into the device via the ETS.

In the case of E-mode compatible KNX devices, a device is normally shipped with loaded
application program. The linking of such KNX devices and the setting of the relevant
parameters is either ensured via appropriate hardware settings or via a central controller.




1 This can be a discrete solution, an ASIC or in case of TP, the so called TP-UART.




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2 Internal structure of a Bus Coupling Unit


+ ‐ (Flash)ROM: System software PEI
RAM: Current values
EEPROM: Application program,
addresses, objects, parameters

Red Black RAM





(Flash)ROM







TRC
µP

EEPROM



µC



KNX


+ ‐

Figure 2: Internal structure of a bus coupling unit

There are two types of KNX bus coupling units:


A BCU with program memory (microcontroller and a transceiver suitable for the
connected medium) and with PEI to the AM.
A BCU without program memory (only a medium specific transceiver with digital
interface to the application microcontroller)

In the different types of a memory of the microcontroller, the following data is stored:

The system software: the different standardised KNX system software profiles (also
referred to as “system stack”) are identified by their “mask version” or “device
descriptor type 0”. A mask cannot be changed. The mask version consists of 2 bytes
where:

 The first digit y refers to the corresponding medium – 0 for TP, 1 for PL110, 2 for
RF and 5 for KNXnet/IP. Not all software profiles are available on all before-said
media.





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 The last digit x refers to the current version of the software profile.
ETS is informed about the underneath mentioned system profiles through the
following mask versions:

2
 y01xh: System 1
 y02xh: System 2
3
 y70xh: System 7
4
 y7Bxh: System B
 y300h: LTE
 091xh: TP Line/backbone coupler – Repeater
 190xh: Media coupler TP-PL110
 2010h: RF bi-directional devices
 2110h: RF unidirectional devices

Unidirectional devices can basically not be configured by ETS. Only e.g. gateways which
communicate with these devices can be configured by ETS. Bi-directional RF-BCUs can
currently not be configured by ETS. The goal is to make this possible as of ETS 5.


Temporary values of the system and the application: These are lost when there is
a bus power down (if not stored earlier in non-volatile memory by the device).

the application program, the physical and group addresses: these are usually
stored in memory that can be overwritten.

In the case of S-mode compatible devices, the manufacturer makes the application
program available to the installer as an ETS product entry, who then loads it into the
device. The manufacturer code of the application program and the bus coupling unit must
match to be able to load the application program.
In the case of E-mode devices, the device reports the supported functionality (as regards
supported “Easy” channels) by means of the device descriptor 2.

























2 previously referred to as BCU 1
3 previously referred to as BCU 2
4 previously referred to as BIM M 112




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+ ‐







Red Black < 18 V Save



RPP 20 V
20 V
5 V
5 V
µC


< 4,5 V Reset
0 V
Receive
Driver Logic Send
Enable


KNX

+ ‐
Bus Coupling Unit

Figure 3: Transceiver


The TP transceiver has the following functions:

Separation or superimposing of the direct current and data
Reverse voltage protection (RPP)
Generation of stabilised voltages of 5 V DC respectively 20 V DC
Initiating a data back-up if the bus voltage drops below 18 V
Triggering a processor reset if the voltage drops below 4,5 V
Driver for transmitting and receiving
Sending and receiving logic
























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3 Type definition of an application module




BCU PEI AM



Analogue 6 R‐Typ
+5 V




2



3

Data 4



7


9


1/10
0 V

5
+5 V +5 V
8
+20 V +20 V







Figure 4: Type definition of an application module
Via a resistor (R-Type) in the application module, the bus coupling unit is able to detect
via pin 6 of the PEI, whether the application module mounted on the BCU fits to the
loaded application program. When the R-Type does not correspond to the one indicated in
the application program, the BCU automatically halts the application program. However,
this rarely applies to more recent bus devices, as for products without a PEI and with a
fully integrated BCU, such a check is no longer required. So, consequently such a PEI
check is mainly limited to flush-mounted bus coupling units. The underneath table gives
an overview of the principal PEI types.










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4 Overview of the most important KNX standardised system
profiles


4.1 System profiles

A system profile can be compared to the operating system of a PC.
The System 1 technology was introduced with the first generation of KNX devices (in
1991), but which is still available. A few years later products based on System 2 and
System 7 were introduced. System 7 was then further developed to System B in order to
get rid of the limitations with regard to the number of group objects and group addresses.
The table below gives an overview of the most important features of these KNX system
profiles:

System 1 System 2/7 System B

Mask version E.g. 0012h E.g. 0025h, 0705h E.g. 07B0h

Maximum number of group objects 12 254 65536
5

Support of interface objects

Support serial number No Yes


Support access control





5 The actual number of available group objects or group addresses which can be assigned
depends on the used microcontroller




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The System 7 technology is especially intended for more complex bus devices, which
assume centralised functions (e.g. application controllers, gateways...).

Application programs designed for System 1 technology can also be loaded into certain
System 2 devices (upwards compatibility).



4.2 Detailed description of the above features

The features of System 2, System 7 and system B outlined above are explained here
again in detail:



4.2.1 Access control
When a tool wants to access memory of System 2, 7 and B devices (reading and/or
writing), it must first get authorisation by means of an authorisation key of 4 byte.
A manufacturer can define keys for such devices: however some of these are reserved for
access to system relevant memory (amongst others the highest access key 0) and are
therefore not communicated to the customers.
The ETS can apply these access mechanisms for not system related memory in the
devices with the before-mentioned system profiles. Access control is never needed for
normal communication via group addresses. In this case, access is always possible.


4.2.2 Serial number

System 2, 7 and System B devices use a serial number: this number, which is assigned to
each device before leaving the factory, allows writing or reading the individual address of
a device without having to press the programming button of the device. This feature is
however not yet supported in ETS.



4.2.3 Interface objects
Interface Objects contain certain system and application properties (e.g. address table,
parameters …), which can be read and/or written by a tool (e.g. ETS during download)
without explicit knowledge of the device’s memory map. The ETS end user cannot
manipulate such objects but can read them by means of the ETS “Device Editor” App.
More in-depth system knowledge explained during the tutor course is required in order to
do this kind of manipulation.


4.2.4 Memory size

When looking at the number of group objects and group addresses one can see that the
memory size increases with the listed mask version: the memory of system 2 is bigger
than 1, and 7 is bigger than 2, especially for profile “B”. For more than 10 years, 255
group objects were considered as a large number but with the development of new touch
panels, application controllers and gateways this number became too small again. That is
why system 7 was extended with 1 byte as regards number of addresses and objects.
Because of this, 65536 and 65535 have now become the maximum values, normally not
reached by current applications. In other words, this is s a pure theoretical value,




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especially when one compares this to the total possible address capacity of a KNX system
(which is just as big).


5 Classical application functions


5.1 Dimming with start/stop telegram



DIMMING ACTUATOR SWITCHES TO LAST REACHED VALUE (PARAMETER DEPENDENT)

100%








0%













START DIMMING STOP DIMMING SWITCH OFF SWITCH ON START DIMMING STOP DIMMING
LONG OPERATION RELEASE DIMMING SHORT OPERATION OF SHORT OPERATION OF
LONG OPERATION RELEASE ROCKER
ROCKER ROCKER ROCKER



Figure 5: Dimming with start/stop telegram

The duration of the rocker operation determines whether the switching function or the
dimming function via the same rocker is activated. If the time the rocker is pressed is
shorter than the time parameterized in the application program of the push button (e.g. <
500 ms), a switch telegram is transmitted. If one operates the rocker longer than the time
parameterized, a 'start dimming' telegram is transmitted. As soon as the rocker is released
again, a 'stop dimming' telegram is transmitted.

Different group addresses are used for the switching and dimming telegrams to ensure
that the dimming actuator executes the correct functions.
















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5.2 Dimming with cyclical telegrams


DIMMING SPEED OF THE ACTUATOR SHALL BE ADAPTED TO THE CYCLICAL TRANSMISSION OF DIMMING TELEGRAMS


Brightness



100%

7/8

6/8
5/8

4/8

3/8

2/8

1/8


Time
+ 12,5 % + 12,5 % + 12,5 % + 12,5 % + 12,5 % + 12,5 % + 12,5 % + 12,5 %

Figure 6: Dimming with cyclical telegrams
In a system controlled by wireless remote controls, e.g. infrared senders, the transmission
signal might be interrupted as somebody passes through the IR beam. In order to avoid a
situation where the dimming actuator does not receive important telegrams (e.g. the stop
telegram), in most cases one will choose the setting 'cyclical dimming' during
parameterisation of a remote control. The transmitter in these settings transmits the
telegram “increase brightness by 12,5 %”. The consequences of losing such a telegram
are not as serious as the loss of a stop telegram, which is only sent once.
































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5.3 Application function: 'dimming actuator'



PEI 230 V AC















SR



0 – 10 V
DAC



20 V
Dimming
5 V
Electronic
BCU AM ballast
Figure 7: Application function: 'dimming actuator'
The counterpart to the sensor function dimming is the dimming actuator. There are
various types of dimming actuators, depending on the dimming concept and the lamps or
the ballasts used. In this example a passive 1 – 10 V analogue interface is shown. But all
dimming actuators have something in common: They have a parameterized dimming
speed. The dimming speed is therefore an exclusive matter of the actuator!

In the example shown above, the BCU transmits a control signal to the application
module. This signal has to be electronically adapted to the control input of the electronic
ballast. The dimmer's electronic ballast uses the voltage to control the light emission of a
fluorescent tube. The relay in the application module is used to (dis)connect the mains
voltage.
























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5.4 Application function: drive control sensor

Start operation of rocker Release rocker
PEI
Brief operation of t1
rocker
Up Down
Telegram Slats 1. level Open/Close
Long operation of t2
rocker


Telegram Blinds
Up/Down
Operation of rocker > Parameterized time
t











BCU AM

Figure 8: Application function: drive control sensor

The blinds but also the shutter operation functions similarly to the dimming operation: A
distinction is made between a brief and a long operation of the rocker.
The time t2 (e.g. 500 ms) acts as a "boundary" between the commands “slats step
open/close” and “blinds up/down”.
T1 is the debouncing time that can be set for push button interfaces and binary inputs. For
push buttons there is normally no debouncing time.

An important difference with dimming is however that if one releases the rocker once the
drive has started, the drive will continue to work until one has again shortly presses the
rocker.

This makes sense as blinds / shutters have basically much longer travel times compared
to the time a dimming actuator needs for to dim up to 100%.

The short operation of the rocker has also two different implications – when the drive is
not in motion, it will cause a moving of the slats (only meaningful for blinds with adjustable
slats). When sending the step command to a moving drive, this will cause the drive to
stop. This shows that in any case for blinds control both commands i.e. shorter or longer
operation of rocker are required, also when there is no need to adjust the slats.













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5.5 Application function: drive control


PEI 24 / 230 V AC















S1











S2





BCU AM





M


Figure 9: Application function: drive control
Depending on the telegram received, the BCU passes on the command “up” or the
command ”down” to the relay S2. On receiving the telegrams “slats open/close 1 step”',
the BCU energises the relay S1 for the appropriate duration. If the motor was already
switched on, this telegram halts the blind (S1 opens). On receiving the telegram “blinds
up/down”, the BCU energises the relay S1 for a period longer than the total time the blind
is in movement from the very top until the very bottom and vice versa. As usual, the limit
switches of the blinds bring the motor to a halt when the limit position is reached, even if
there is still voltage at the motor.

A blind actuator never has the task to take care of the safe deactivation of the blinds. This
always needs to be ensured by the device itself in order to guarantee interlocking!













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6 Drive control object structure



Telegram from:

Automatic Group 2/1/31 Group object table
Push button Group 2/1/12, 2/1/13
Wind sensorGroup 2/1/99 2/1/31
2/1/99 2/1/13
2/1/12

Object 1 Object 2 Object 3
SAFETY UP / DOWN SLATS

Telegram gale: Telegram blinds Telegram slats
Blinds control disabled Up / Down Up / Down
Blinds e.g. Up (Long operation) (Short operation)
Object value = 1


Telegram gale end:
Control enabled
Object value = 0

Gate: Open when 0 Gate: Open when 0
Object value = 1:
Up
Disable normal operation
Execution

Figure 10: Drive control object structure
The figure above shows the basic functionality of a blind actuator. Apart from the normal
operation each blind/shutter actuator can for instance have a safety function.
If, for example, the sensor responsible for measuring the position of the sun triggers the
telegram “blinds down” using the group address 2/1/31, the object group "up/down" is
addressed and the corresponding command is executed.
Brief operation of the push button transmits the 2/1/13 telegram “adjust slats” and long
operation of the key sensor sends the 2/1/12 telegram “open/close blinds completely”.
Telegram 2/1/99 triggered by the wind sensor addresses the object group “safety”. If a
gale is developing, telegram 2/1/99 orders the blinds to go up/down (depending on the
parameterization) and disables any further operation. When the storm has eased off, a
telegram is sent that enables blind operation again. The de-activation of the alarm does
not mean that the actuator is lowering the blinds again by itself (in the position before the
gale). This makes no sense as the actuator has no information about the duration of the
alarm or whether the blind really has to go down again.

New actuators have of course a variety of further functions and group objects, which
cannot be explained during the basic course due to time constraints. These more complex
functionalities, e.g. weather station, are explained in detail in the advanced course.












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Table of Contents

1 Safety Low Voltage Networks ...................................................................................... 3
2 SELV Safety Extra Low Voltage Network .................................................................... 4
3 Types of Bus cable ...................................................................................................... 5
4 Installation of cables .................................................................................................... 7
5 Bus Devices in distribution boards ............................................................................... 8
6 Power supply unit ........................................................................................................ 9
7 Power supply for two lines ......................................................................................... 11

7.1 Two power supply units in one line .................................................................... 12

8 Distributed power supply ........................................................................................... 13
9 Bus cables in wall boxes ............................................................................................ 14
10 Installation of flush-mounted bus devices .................................................................. 15
11 Standardised TP Bus connector ................................................................................ 16
12 Lightning protection measures ................................................................................... 17
13 Bus cables installed between buildings ..................................................................... 19
14 The prevention of loops ............................................................................................. 20
15 Basic immunity of bus devices ................................................................................... 21
16 Bus devices on cable ends ........................................................................................ 21
17 The overvoltage arrester terminal .............................................................................. 22
18 Recommendations to the use of overvoltage arresters ............................................. 23
19 Checking the installation ............................................................................................ 24
20 Information to the use of data rails ............................................................................ 26
21 Power supply unit with data rail ................................................................................. 27
22 Power supply unit for two lines with data rail ............................................................. 28




































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1 Safety Low Voltage Networks


SELV (Safety Extra Low Voltage)


 Safety transformer

 Voltage range less than/
identical to 120 V DC or 50 V AC
 Safe insulation to e.g.
230 / 400 V AC

 SELV may not be earthed!





Figure 1: Safety Low Voltage Networks
General: for the bus and mains installation the relevant installation requirements of
the respective country shall be observed.

SELV stands for Safety Extra Low Voltage

Clearance and creepage distances: The clearance and creepage distances indicated
above apply for:

Pollution degree 2 (offices)
Overvoltage category 3 (permanently connected to mains, high availability)
Insulation material class 3

Permitted voltage range:

Alternating current (AC):  50 V
Direct current (DC):  120 V

No special protection against direct contact is required if the voltages do not exceed 25 V
AC or 60 V DC.

Earthing:
A SELV network may not be earthed!






















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2 SELV Safety Extra Low Voltage Network






User


No insulation

Other networks
Mains network SELV – Network E.g.
230 / 400 V for KNX: 30 V DC
telecommunication






PE





Safe insulation Basic insulation


Figure 2: SELV Safety Extra Low Voltage Network
A power supply with secure mains separation generates the SELV voltage for the KNX TP
bus.

Voltage used:
30 V DC

Insulation:
Safe insulation from other networks.
Basic insulation to earth.
No insulation on the user’s side.

Attention:

The SELV network may not be earthed!
Cables that are intended for the installation of mains networks may not be used for the
installation of TP networks!




















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3 Types of Bus cable


YCYM 2×2×0,8
‐ Fixed installation: dry, humid and wet rooms; wall‐mounted, flush‐mounted, in conduits;
‐ Outdoor: If protected against direct sun radiation;
‐ Test voltage: 4 kV according to EN 50090


J‐Y (St) Y 2×2×0,8

‐ Fixed installation: dry and humid industrial sites; wall‐mounted, flush‐mounted, in conduits;
‐ Outdoor: Flush‐mounted and conduits
‐ Test voltage: 2,5 kV according to EN 50090


Synthetic Material Tracer




‐ (white)
KNX + (yellow)

‐ BUS (black)
Synthetic foil + BUS (red)
Metalised synthetic foil




Figure 3: Types of bus cable
Cable fulfilling the KNX requirements in volume 9 of the KNX Specifications (e.g. YCYM
2×2×0,8 or J-Y(St)Y 2×2×0,8 in TP design) can be approved (without KNX logo) or
1
certified (with KNX logo) by KNX Association .
Only the standard green KNX TP cable guarantees:
max. cable length of a line
max. distance between two bus devices in a line
max. number of bus devices per line
The requirements for instance include a loop resistance of 75  and a loop capacitance of
100 nF per 1000 m. For all other cables types, the maximum length given in the data
sheet of the cable must be observed.

Normally, it is not necessary to connect the shielding of the cables.

















1 For the current list of KNX certified/approved cable types, please consult the KNX web site
(www.knx.org)

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When installing a standard cable with a test voltage of 4 kV, the following conditions
apply.

Used wire pair:
Red: plus
Black: minus

Spare wire pair: Permitted use of the spare wire pair:
no connection at all
for other SELV low voltage networks


Test voltage according to EN 50090:
The specified test voltage must be applied to all connected wire cores (shielding drain
wire included) and the outer surface of the cable sheath.


Note:
Please make sure that all installed cables are properly identified and marked!
























































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4 Installation of cables


230 V e.g. NYM
Overall insulated single core
230 V adjacent to the sheath of
KNX TP
the bus cable
YCYM or J‐Y(St)Y (2,5 kV)

KNX TP
YCYM or J‐Y(St)Y (2,5 kV)
Overall insulated single core of
the bus adjacent to the sheathed
* mains cable

230 V e.g. NYM



230 V e.g. NYM


Exposure of two single cores
KNX TP
*
* identical insulation
YCYM or J‐Y(St)Y (2,5 kV) >= 4 mm separation or
Figure 4: Installation of cables
The requirements for the installation of bus cables are generally the same as for the
installation of 230/400 V AC networks.

Special requirements:

Insulated wire cores of sheathed mains cables and KNX TP bus cables may be
installed next to each other without any clearance space.
A minimum clearance space of 4 mm must be observed between the insulated wire
cores of KNX TP bus cables and those of sheathed 230 V AC mains cables.
Alternatively, the wire cores must be provided with an equivalent insulation, such as a
spacer or insulation sleeving. This also applies to wire cores of other cables that are
not part of SELV/PELV circuits.
An adequate distance to the external lightning protection system (lightning arrester)
must be ensured.
All cables should be permanently marked as KNX TP or BUS cables.

A terminating resistor is not required.















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5 Bus Devices in distribution boards


Standardised power Requirements
distribution boards


50 U
 Use of standardised distribution
boards

 Install bus cables with sheath up to
the terminal


 Do not install bus devices above mains
devices with significant power losses


 Cover unused section of data rail









Figure 5: Bus devices in distribution boards

Any commercial, standardised electric power distribution board equipped with EN 50022
35x7.5 mm DIN rails may be used, on which KNX TP DIN rail mounted devices can be
mounted.
Some of these KNX TP DIN rail mounted devices use spring contact blocks to a standard
data rail glued into DIN rails, others have the normal bus connector (see below) for
connection to the bus.

When using data rails unused parts of the data rail must be protected by cover strips.
If the mains section is separated from the bus installation, no special installation
requirements need to be observed.
If the mains section is not separated from the bus installation, the bus cables must be
sheathed up to the terminals.
Possible contact between mains cores and bus cable cores must be prevented by
adequate wiring and/or mounting.

Bus devices should not be mounted above mains devices with significant power losses,
as this could cause excessive heat development in the installation.
When a lightning arrester is installed on a DIN rail containing a data rail, the following
requirements must be met:

Overall insulation of the arrester (e.g. no use of uncovered air spark gaps).
As DIN rails may not be used for earthing, arresters must have a separate earthing
terminal.







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6 Power supply unit


TP Connector



DVC DVC
>= 21 V DC >= 21 V DC
230 V
50/60 Hz

Power supply unit / Choke
Bus line
> 100 ms
30 V DC 640 mA
buffer


Figure 6: Power supply unit (with TP connectors)

Note: if not explicitly said below, the following applies to centralised power supply units.

Power supply units produce and monitor the system voltage of 30 V DC necessary for the
operation of a KNX TP installation.
Each line needs an own power supply unit to supply the connected bus devices.
The power supply unit has an integrated voltage and current control and is therefore
resistant to short circuits.

The power supply unit is able to bridge short power gaps of minimum 100 ms.

Bus devices require a minimum of 21 V DC for safe operation. The energy demand of the
device can be read in the data sheet of the respective manufacturer.




































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Example of a power supply unit Features


 Earth connection prevents static
230 V charging

 100 ms buffer time bridges brief
interruptions of the mains
L N DIN‐Rail
Mains
 Optional LEDs for displaying
Technical information Power Supply Unit
230 V 30 V DC Overload Overload
50...60 Hz Mains Mains
0...45 °C Overvoltage Overvoltage
 Additional output for supplying other
Ancillary voltage KNX voltage
line (needs extra choke !)

Figure 7: Example and features of a power supply unit (on DIN rail without data rail)


To prevent from static charges on the bus side, the power supply unit includes high ohmic
resistances connected from each bus core to earth. The power supply unit should be
earthed. To do so, connect the earth point of the low voltage installation to the power
supply unit. This connection should be marked yellow/green. This does not result in
protective effects according to safety regulations and does not contradict the conditions
that apply for SELV networks.

Some power supply types or external chokes have a reset switch and a red control LED.
The connected line can be set to 0 V with this switch. The chokes prevent the short-
circuiting of bus telegrams (alternating voltage 9600 Hz) by the DC controller of the power
supply unit.

Many types of power supply units are available, depending on the supplied output current
(160 mA, 320 mA, 640 mA). It goes without saying that the number of installable devices
in a line depends on the type of PSU used and the individual power consumption of the
devices in that line. Some PSU types have an integrated choke; some need an additional
external choke.

Modern power supply units are DIN rail mounted, whereby the bus voltage is available via
an included bus connector. Some types have an ancillary voltage output, with which it is
possible to supply other lines using a separate choke. Uninterruptible power supply types
are also available. Some PSU types have a floating relay output providing information
about normal operation/mains failure for evaluation purposes. Most of the PSU types have
LEDs, indicating the operating mode of the power supply unit e.g.

Green: The power supply is active.
Red: The power supply unit is overloaded, possibly due to a short circuit between bus
wires.
Yellow: An external voltage higher than 30 V has been applied to the bus side.









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